Question

. cos 4 x = cos 2 x find the value of x​

Answer 1

Answer:

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Kindly refer to the attachment.

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Answer 2

Using Trigonometric identities: Cos2x = 1- Sin2x

Cos2x = 1 – (4/5)2

= 1 – 16/25

= (25 – 16) / 25

= 9/25

Cos x = 9/25−−−−√= 3/5

Example 2: If Sec x = 4/7, find the Cos x?

Solution: As cos x = 1/sec x

Therefore, cos x = 1/ 4/7

= 7/4