Question

Plez the answer the subject is the double angle and half angle formula

Answer 1

cos 2x = (√7) / 4

Explanation:

sin x - cos x = 1/2

(sin x - cos x)² = (1/2)²

sin²x - 2 sin x cos x + cos² x = 1/4

1 - 2 sinx cosx = 1/4

2 sinx cosx = 3/4

sin 2x = 2 sinx cosx = 3/4

sin² 2x = 9/16

cos² 2x = 1 - sin² 2x = 1 - 9/16 = 7/16

cos 2x = (√7) / 4