Question

if Cos x=3/5,find the exact value of Cos 2x

Answer 1

Step-by-step explanation:

Given that cos x=3/5

formula of cos 2x = 2 cos square x- 1

2(3/5)square -1 = 2 (9/25)-1

= 18/25-1= -7/25

cos 2x = -7/25

Hence the exact value of cos 2x = -7/5