Question

\( 8 \cos^4 x - 8 \cos^2 x + 1 \) is equal to

• A. \( \cos 4x \)
• B. \( \sin 4x \)
• C. \( \cos 2x - \sin 4x \)
• D. \( \cos 2x + \sin 4x \)

Hint:

Use standard trigonometric identities to simplify higher powers of trigonometric functions.

Answer 1

The Correct Option is A

Using the trigonometric identity for \( \cos^2 x \), we simplify: \[ 8 \cos^4 x - 8 \cos^2 x + 1 = \cos 4x \] Thus, the correct answer is \( \cos 4x \).