Question

Given that cos (x) = k
what does cos (2x) = ?

Thanks in advance :)

Answer 1

(2x) = 2k

Explanation:

If x = k, then 1x=1k, then 2x=2k

Answer 2

2k² - 1

Explanation:

cos x =k

cos 2x = 2 cos ² x - 1

= 2k² - 1