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More Lessons for PreCalculus

Math Worksheets

Examples, solutions, videos, worksheets, games and activities to help PreCalculus students learn how to use the half angle or double angle formula in some examples.

The following diagrams show the half-angle identities and double-angle identities. Scroll down the page for more examples and solutions on how to use the half-angle identities and double-angle identities.

**Half-Angle Identities**

Example:

1. Determine the exact value of sin (π/8)

2. Determine the exact value of cos (105°)

3. Given cos A = -2/3 in quadrant II, determine cos(A/2), sin(A/2) and tan(A/2).

**Double-Angle Identities**

Example:

1. If sin A = 3/5 in quadrant II, find the exact value of cos(2A), sin(2A) and tan(2A). Then determine the quadrant of angle 2A.

2. Determine cos(A) given cos(2A) = -3/4 and terminates in quadrant III.**Rewrite a Trigonometric Expression Using a Half Angle Identity**

Example:

Rewrite the following trigonometric expression using a half angle identity.

1. (sin(5x))^{2}

2. (cos(2x))^{4}
**Solve a Trigonometric Equation Using a Double Angle Identity**

Example:

Solve on the interval [0,2π).

cos(2x) = cos(x)

**How to solve a Trigonometric Equation Using a Double Angle Identity?**

Example:

Solve on the interval [0,2π).

sin(2x) = 2cos^{2}(x)

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

More Lessons for PreCalculus

Math Worksheets

Examples, solutions, videos, worksheets, games and activities to help PreCalculus students learn how to use the half angle or double angle formula in some examples.

The following diagrams show the half-angle identities and double-angle identities. Scroll down the page for more examples and solutions on how to use the half-angle identities and double-angle identities.

Example:

1. Determine the exact value of sin (π/8)

2. Determine the exact value of cos (105°)

3. Given cos A = -2/3 in quadrant II, determine cos(A/2), sin(A/2) and tan(A/2).

Example:

1. If sin A = 3/5 in quadrant II, find the exact value of cos(2A), sin(2A) and tan(2A). Then determine the quadrant of angle 2A.

2. Determine cos(A) given cos(2A) = -3/4 and terminates in quadrant III.

Example:

Rewrite the following trigonometric expression using a half angle identity.

1. (sin(5x))

2. (cos(2x))

Example:

Solve on the interval [0,2π).

cos(2x) = cos(x)

Example:

Solve on the interval [0,2π).

sin(2x) = 2cos

Rotate to landscape screen format on a mobile phone or small tablet to use the **Mathway** widget, a free math problem solver that **answers your questions with step-by-step explanations**.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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