Precalculus : Double-Angle Identities

Study concepts, example questions & explanations for Precalculus

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Example Questions

Example Question #1 : Double Angle Identities

Find the exact value

.

Possible Answers:

Correct answer:

Explanation:

By the double angle formula

Example Question #2 : Double Angle Identities

Find the exact value

.

Possible Answers:

Correct answer:

Explanation:

By the double angle formula

Example Question #3 : Double Angle Identities

Find the exact value

.

Possible Answers:

Correct answer:

Explanation:

By the double-angula formula for cosine

For this problem

Example Question #4 : Double Angle Identities

Find the exact value

.

Possible Answers:

Correct answer:

Explanation:

By the double-angle formula for the sine function

we have

thus the double angle formula becomes,

Example Question #5 : Double Angle Identities

If , which of the following best represents ?

Possible Answers:

Correct answer:

Explanation:

The expression  is a double angle identity that can also be rewritten as:

Replace the value of theta for .

The correct answer is: 

Example Question #6 : Double Angle Identities

Which expression is equivalent to  ?

Possible Answers:

Correct answer:

Explanation:

The relevant trigonometric identity is:

In this case, "u" is since .

The only one that actually follows this is

 

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