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**Standards**:

- TF-A.1. Understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle.
- TF-A.2. Explain how the unit circle in the coordinate plane enables the extension of trigonometric functions to all real numbers, interpreted as radian measures of angles traversed counterclockwise around the unit circle.
- TF-A.3. (+) Use special triangles to determine
geometrically the values of sine, cosine, tangent for π/3, π/4 and π/6,
and use the unit circle to express the values of sine, cosine, and
tangent for
*x*, π +*x*, and 2π –*x*in terms of their values for*x*, where*x*is any real number. - TF-A.4. (+) Use the unit circle to explain symmetry (odd and even) and periodicity of trigonometric functions.

**Technology-enhanced investigations:**

Mathwords.com: Math Dictionary: Key vocabulary for this domain. Use with TF-A, TF-B, TF-C:

A. Dendane: Analyze Math:

- Unit Circle and the Trigonometric Functions sin(x), cos(x) and tan(x): This tutorial helps learners understand domain, range, and possible asymptotes of these trig functions. It contains the HTML5 Applet to Explore the Unit Circle and Trigonometric Functions, which visually generates the sine, cosine, and tangent graphs as a point moves counterclockwise around the unit circle .
- HTML5 Applet to Explore Angles in Standard Position: Learners can enter two angles and explore their relationship on the unit circle, which also shows coordinates of points of key angles referenced to 30-45-60-90 degrees.

DadsWorksheets.com: Online calculator to convert degrees to radians (or radians to degrees) with visual on a circle. It includes math content to explain the theory. Aligns with TF-A.2.

Geogebra.org:

- Trigonometric Graphs and the Unit Circle: Help students develop a sound understanding of the three basic trigonometric functions using the unit circle as a reference. Learners can also see reciprocal trig functions.
- The Unit Circle: Learns can generate values of all six trig functions as a point moves around the unit circle. The applet is shown in degrees.
- The Unit Circle exact values generated for angles in radians and degrees.
- Ferris Wheel Unit Circle: Create a graph of the height of a seat on a Ferris wheel to explore the sine function and characteristics of the unit circle. Users can pivot the Ferris wheel to emphasize the change in height of a seat, show the sine and cosine functions, turn on coordinates, degrees, and/or radians associated with the eight benchmark points on the unit circle, and see values for sine, cosine, and tangent of the seat position.

Khan Academy:

- Unit circle definition of trig functions: video: Aligns with TF-A.2.
- Basic trigonometric identities: 4 videos on the symmetry and periodicity of the sine, cosine, and tangent functions: Aligns with TF-A.4.

LearnZillion:

- Lesson set: Extend trigonometric functions to all real numbers using the unit circle. Five video lessons: Understanding the wrapping function using the unit circle, find trig values for angles using reference triangles, understand quadrantal angles by examining x and y values near them, graph f(x) = sinx and g(x) = cosx using the unit circle, graph trig functions using a graphing calculator. Aligns with TF-A.2.
- Lesson set: Explain how the unit circle in the coordinate plane enables the extension of trigonometric functions to all real numbers. Six video lessons: Find trig ratios of angles in the coordinate plane, find values of trig functions using the unit circle, determine the signs of trig functions by identifying coordinate signs, evaluate trig functions of angles in all four quadrants; find sine, cosine, tangent of angles on the x and y axes, determine the domain of the six trig functions using ratio denominators. Aligns with TF-A.2.
- Lesson set: Choose trigonometric functions to model periodic phenomena. Five video lessons: Graph the sinusoidal functions by plotting points; stretch and transform by shifting sinusoidal functions horizontally and vertically; graph tangent, secant, cosecant, cotangent by drawing sine and cosine graphs; model periodic phenomena using the trigonometric functions. Aligns with TF-A.4.

Mathispower4u: Trigonometry Videos is an extensive collection on nearly every topic in trig from James Sousa. Aligns with TF-A, TF-B, and TF-C.

NCTM Illuminations: Pi Fight: Get comfortable with radians and degrees. Aligns with TF-A.

PatrickJMT: A Way to Remember the Entire Unit Circle for Trigonometry. Video.

PhET Interactive Simulations: Trig Tour. This simulation shows the relationship between the unit circle and the graphs of the trig functions. You can explore it in either degrees or radians. It also examines trig values of special angles. Aligns with TF-A.2, TF-A.3, and TF-A.4.

Teaching Channel Video: Ferris Wheel: Trigonometric Functions. Lesson objectives: Model how a trigonometric function describes the relationship of a Ferris wheel rider as the wheel spins at a constant rate with relationship to the height of the rider from the ground. Discern the relationship between the given measure and the period, phase, offset and amplitude of a cosine function. Questions for learners to consider are included. Use with BF-A.1.b, BF-B.3, and TF-A.1.

Thinking Mathematics:

- Radian Measure: A YouTube video with explanation of the radian measure. Aligns with TF-A.1.
- 30-60-90 and 45-90-45 Triangles: A YouTube video on “special” triangles. Aligns with TF-A.3.

Walter Fendt: Math Applets: Sine, Cosine, and Tangent of an Angle: Use this applet to demonstrate how the graphs of these functions are generated as a point moves counterclockwise around the unit circle.

Wisc-Online, Learning Object: Learn to Count by Common Radian Units: After students learn what a radian measure is and have derived key values of the coordinates associates with common radian units (e.g., π/3, π/4, and π/6), this activity will provide practice finding those values on a unit circle. Students do not need to know the definitions of the trig functions to do this activity. This activity works well with standard TF-A.3.

Wolfram Demonstrations Project: Download the free Wolfram CDF player to interact with the following manipulatives. Note: Within the Wolfram Demonstration Project are 4 manipulatives addressing TF-A.1, 19 manipulatives for TF-A.2 (all are relevant), 18 manipulatives for TF-A.3, and 16 manipulatives for TF-A.4. Among those:

- Angles measured in degrees and radians: Aligns with TF-A.1 and TF-A.2.
- Find the exact value of an angle: Aligns with TF-A.1.
- Wrapping the number line around the unit circle: Aligns with TF-A.1.
- Trigonometry in quadrant 1: Aligns with TF-A.2.
- Sine, cosine, tangent and the unit circle: Aligns with TF-A.2.
- Illustrating trigonometric curves with the unit circle (6 trig functions): Aligns with TF-A.2.
- Most common angles: Aligns with TF-A.3.
- Illustrating Sine with the Unit Circle: Aligns with TF-A.3 and TF-A.4.
- Illustrating Cosine with the Unit Circle: Aligns with TF-A.3 and TF-A.4.
- Illustrating Tangent with the Unit Circle: Aligns with TF-A.3 and TF-A.4.
- Illustrating Cotangent with the Unit Circle: Aligns with TF-A.3 and TF-A.4.
- Illustrating Secant with the Unit Circle: Aligns with TF-A.3 and TF-A.4.
- Illustrating Cosecant with the Unit Circle: Aligns with TF-A.3 and TF-A.4.

**Multiple Choice:**

ACT Academy and OpenEd:

- Radian measures TF.1: 5 multiple choice questions. Includes related review resources. Aligns with TF-A.1.
- Unit circle and trigonometric functions TF.2: 5 multiple choice questions. Includes related review resources. Aligns with TF-A.2.
- Special right triangles TF.3: 5 multiple choice questions. Includes related review resources. Aligns with TF-A.3.
- Symmetry and periodicity of trigonometric functions TF.4 : 5 multiple choice questions. Includes related review resources. Aligns with TF-A.4.

Wisc-Online, Learning Object: What is a Radian?: This is a short interactive demonstration of the size of a radian and the number of radians in a circle, accompanied by three multiple choice problems to test understanding.

**Constructed-response:**

Khan Academy: Practice questions with videos.

- Radians and arc length: Aligns with TF-A.1.
- Trigonometric values of special angles: Aligns with TF-A.3.

The Math Page: Trigonometry: Aligns with TF-A.

- Arc Length: Lesson introduces the definition of the radian and includes practice problems. Use with TF-A.1.
- Radian Measure. Lessons on converting degrees to radians, radians to degrees, coterminal angles, and the multiples of π with practice problems. Use with TF-A.2.
- Analytic Trigonometry: The Unit Circle: Lesson on how right triangle trig can extend to definitions of the trig functions of angles drawn on a circle. It includes the "signs" of the trig functions in each quadrant, quadrantal angles, and the unit circle. Practice problems are included. Use with TF-A.4.
- Trig Functions of Any Angle

**Performance tasks:**

Georgia Standards of Excellence Framework:

- Pre-Calculus Unit 1: Introduction to Trigonometric Functions. This unit contains 13 tasks, including a Culminating Task: Graphing Other Trigonometric Functions. Tasks align to TF-A.1, TF-A.2, TF-B.5, TF-C.8 and IF-B.4, IF-C.7.
- Pre-Calculus Unit 2: Trigonometric Functions. This unit contains two tasks: Right Triangles and the Unit Circle, and Inverse Trigonometric Functions. Tasks align to BF-B.4, BF-B.4.d, TF-A.3, TF-A.4, TF-B.6, TF-B.7 and are also related to TF-A.2, TF-B.5, and IF-C.7.e.

Mathematics Assessment Project: Standards: High School: Functions: https://www.map.mathshell.org/stds.php?standardid=1448 Task 427: Ferris Wheel Aligns with TF-A.

Mathematics Vision Project, Secondary 3 Student Edition:

- Module 6: Trigonometric Functions: This module contains 13 classroom tasks. Function standard TF-A.1 is found in tasks 5-9; TF-A.2 is found in task 3, tasks 5-9, and task 13. Task 13 also addresses TF-A.3, TF-A.4.

**Standards**:

- TF-B.5. Choose trigonometric functions to model periodic phenomena with specified amplitude, frequency, and midline.
- TF-B.6. (+) Understand that restricting a trigonometric function to a domain on which it is always increasing or always decreasing allows its inverse to be constructed.
- TF-B.7. (+) Use inverse functions to solve trigonometric equations that arise in modeling contexts; evaluate the solutions using technology, and interpret them in terms of the context.

**Technology-enhanced investigations:**

A. Dendane: Analyze Math:
Sine
Function and
Cosine
Function: HTML5 applets to explore properties of graphs of the sine
function and cosine function. These applets help learners to
understand the meaning of amplitude, frequency, shifts left or right,
and midline by changing parameters in equations of the form *f(x) = a
sin (bx + c) + d * and of the form *f(x) = a cos (bx +
c) + d. *The x-axis in each applet is labeled with radians.
Use with TF-B.5.

Mathispower4u: Trigonometry Videos is an extensive collection on nearly every topic in trig from James Sousa. Aligns with TF-A, TF-B, and TF-C.

NCTM Illuminations:
Trigonometric Graphing: Learners can investigate
amplitude, period, and phase shift by examining the graphs of various
trigonometric functions (sin, cos, tan, sec, csc, cot) for equations of
the form *f(x) = a sin (bx + c) + d.* They can change the
function and parameters a, b, c, and d, and choose to display graphs in
either degrees or radians. Use with TF-B.5.

Wolfram Demonstrations Project: Download the free Wolfram CDF player to interact with the following manipulatives. Note: Within the Wolfram Demonstration Project are 7 manipulatives addressing TF-B.5 and 3 manipulatives for TF-B.6. Among those:

- Sine waves for musical scales: Aligns with TF-B.5.
- The sound of sine waves: Aligns with TF-B.5.
- Domain and range of inverse trig functions: Aligns with TF-B.6.

PatrickJMT: Videos on Inverse Trig Functions.

- Inverse Trig Functions, Part 1 (Basic Introduction). Use with TF-B.6.
- Inverse Trig Functions, Part 2 and Inverse Trig Functions, Part 3 (Evaluating Inverse Trig Functions). Use with TF-B.7.
- Inverse Trig Functions, Part 4 (Simplify the Expression using Right Triangle). Use with TF-B.7.

**Multiple Choice:**

ACT Academy and OpenEd:

- Modeling with trigonometric functions TF.5: 5 multiple choice questions. Includes related review resources. Aligns with TF-B.5.
- Inverse trigonometric functions TF6 -TF.7: 5 multiple choice questions. Includes related review resources. Aligns with TF-B.6 and TF-B.7.

MathsIsFun.com: Tutorial on the Inverse Sine, Cosine, Tangent. Examples are shown. Learners then complete 10 multiple choice problems. Aligns with TF-B.6 and TF-B.7.

Wolfram Demonstrations Project: Download the free Wolfram CDF player to interact with the following manipulative: Elementary Transformations of a Sine Wave Quiz: Learners are shown a sine graph and a transformation of it. They select parameters to create the equation of the transformation. Aligns with TF-B.5.

**Constructed-response:**

Khan Academy: Practice questions with videos.

- Modeling with periodic functions: Aligns with TF-B.5.
- Modeling with periodic functions-2, Level 2 with phase shift: Aligns with TF-B.5.
- Understanding inverses of functions: Aligns with TF-B.6.
- Inverse trig word problems: Aligns with TF-B.7.

NRICH: Tangled Trig Graphs: Learners are presented multiple sine graphs on the same set of axes and are challenged to determine the equations from the graphs and how they might also be written in terms of the cosine function. "The problem gives the opportunity to investigate reflections, stretches and translations of curves, and the corresponding effects on equations" (Teachers' Resources for this problem). Aligns with TF-B.5.

Wolfram Demonstrations Project:
Download the free Wolfram CDF player
to interact with the following manipulative:
Inverse Function of a Trigonometric Function Game:
This Demonstration provides a game for the exact
calculation of f^{-1}(f(x)) for trigonometric functions. Aligns
with TF-B.6 and TF-B.7.

**Performance tasks:**

Georgia Standards of Excellence Framework:

- Pre-Calculus Unit 1: Introduction to Trigonometric Functions. This unit contains 13 tasks, including a Culminating Task: Graphing Other Trigonometric Functions. Tasks align to TF-A.1, TF-A.2, TF-B.5, TF-C.8 and IF-B.4, IF-C.7.
- Pre-Calculus Unit 2: Trigonometric Functions. This unit contains two tasks: Right Triangles and the Unit Circle, and Inverse Trigonometric Functions. Tasks align to BF-B.4, BF-B.4.d, TF-A.3, TF-A.4, TF-B.6, TF-B.7 and are also related to TF-A.2, TF-B.5, and IF-C.7.e.

Illustrative Mathematics: Functions: Foxes and Rabbits 2: This task aligns with standard TF-B.5.

Mathematics Vision Project, Secondary 3 Student Edition:

- Module 6: Trigonometric Functions: This module contains 13 classroom tasks. Function standard TF-B.5 is found within tasks 1, 2, 4, 5, 10-12.

NCTM's Reasoning and Sense Making Task Library: Tidal Waves includes the task overview, teacher notes for its use in the classroom, and student activity sheet. Aligns with BF-B.3, TF-B.5 and mathematical practice standards 1 and 7.

**Standards**:

- TF-C.8. Prove the Pythagorean identity sin
^{2}(θ) + cos^{2}(θ) = 1 and use it to find sin(θ), cos(θ), or tan(θ) given sin(θ), cos(θ), or tan(θ) and the quadrant of the angle. - TF-C.9. (+) Prove the addition and subtraction formulas for sine, cosine, and tangent and use them to solve problems.

**Technology-enhanced investigations:**

Purple Math: Trigonometric Identities: This is a list of all the basic trigonometric identities, which can be used in solving problems.

YouTube:
Pythagorean Identity Proofs: This is a playlist that features
seven videos on how to prove the Pythagorean identity sin^{2}(θ)
+ cos^{2}(θ) = 1 and using it to find sin(θ), cos(θ),
or tan(θ) given sin(θ), cos(θ), or tan(θ) and the quadrant of the
angle. Aligns with TF-C.8.

Khan Academy: Videos posted at YouTube, which align with TF-C.9:

- Proof of sin(a + b): sin(a+b) = (sin a)(cos b) + (cos a)(sin b)
- Proof of cos(a + b): cos(a+b) = (cos a)(cos b) - (sin a)(sin b)

Law of Sines and Law of Cosines are two applets that allow you to input sides and angles per each law and then each applet calculates the missing sides and angles in a triangle. Some practical applications of each law are also included. These are hosted by the Department of Physics and Astronomy at Georgia State University.

Mathispower4u: Trigonometry Videos is an extensive collection on nearly every topic in trig from James Sousa. Aligns with TF-A, TF-B, and TF-C.

Omnicalculator.com: Trigonometry calculators address law of sines, law of cosines, trig function values . Explanation of theory is included for each. Use with TF-C.9.

PatrickJMT: Videos using addition and subtraction formulas for sine, cosine, and tangent to solve problems. Each aligns with TF-C.9:

- Identities for Sum and Differences of Sine and
Cosine: Video examples showing use of these formulas: Example 1: sin(75
^{o}); Example 2: cos(15^{o}); Example 3: tan(165^{o}) written as sin(165^{o})/ cos(165^{o}). - Sum and Difference Identities to Simplify an Expression, Example 2: This example uses tan(x + y) to simplify tan(x + 4π).

Wolfram Demonstrations Project: Download the free Wolfram CDF player to interact with the following manipulatives. Note: Within the Wolfram Demonstration Project are 3 manipulatives addressing TF-C.8 and 9 manipulatives for TF-C.9. Among those:

- Two visual proofs of a basic trigonometric identity: the Pythagorean identity. Aligns with TF-C.8.
- Trig functions for a right triangle: Aligns with TF-C.8.
- Cofunction Identities for Sine and Cosine: This is a visual demonstration using the definition of each function on a right triangle to show the sine of an angle = cosine of its complement and the cosine of an angle = sine of its complement. Use with TF-C.9.
- Difference Formula for Cosine: This is a visual demonstration of the formula cos(A-B) = cos(A)cos(B) + sin(A)sin(B). Take time to justify the steps in the explanation and label parts sin(A), cos(A), sin(B), cos(B) on both figures. It's easier to understand the proof from the figures when angles A and B are not equal. Aligns with TF-C.9.
- Addition Formula for Sine: This is a visual demonstration of the formula sin(A+B) = sin(A)cos(B) + cos(A)sin(B). Take time to justify the steps in the explanation and label parts sin(A), cos(A), sin(B), cos(B) on both figures. It's easier to understand the proof from the figures when angles A and B are not equal. Aligns with TF-C.9.

**Multiple Choice:**

ACT Academy and OpenEd:

- Pythagorean identity with applications TF.8: 4 multiple choice questions. Includes related review resources. Aligns with TF-C.8.
- Sum and Difference Formulas TF.9 for sine and cosine: 4 multiple choice questions. Includes related review resources. Aligns with TF-C.9.

Khan Academy: Practice questions with videos.

- Find trig values using angle addition identities: Aligns with TF-C.9.

**Constructed-response:**

Khan Academy: Practice questions with videos.

- Circles and Pythagorean identities: Aligns with TF-C.8.
- Use the Pythagorean Identity: Aligns with TF-C.8.
- Using the trig angle addition identities: Aligns with TF-C.9.

**Performance tasks:**

Georgia Standards of Excellence Framework:

- Pre-Calculus Unit 1: Introduction to Trigonometric Functions. This unit contains 13 tasks, including a Culminating Task: Graphing Other Trigonometric Functions. Tasks align to TF-A.1, TF-A.2, TF-B.5, TF-C.8 and IF-B.4, IF-C.7.
- Pre-Calculus Unit 4: Trigonometric Identities. This unit contains eight tasks: Proving the Sine Addition and Subtraction Identities, Proving the Cosine Addition and Subtraction Identities, A Distance Formula Proof for the Cosine Addition Identity, Proving the Tangent Addition and Subtraction Identities, Double-Angles Identities for Sine, Cosine, Tangent; Cosine Double-Angle: A Man with Many Identities; Deriving Half-Angle Identities, and a Culminating Task: How Many Angles Can You Find? Tasks align to TF-C.9.

Common Core Math:
Intro | HS Functions Domain:
IF | BF | LE | **TF** |