Answer:
cos 2x = (√7) / 4
Step-by-step 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
