Question

Jika tan x = 5/12, maka nilai cos 2x adalah

Answer 1

Verified answer

Trigonometri.

tan x = b / a = 5/12
c = √(a² + b²) = √(12² + 5²) = 13
sin x = b / c = 5 / 13
cos x = a / c = 12 / 13

cos 2x = cos² x - sin² x = 1 - 2 sin² x = 2 cos² x - 1
cos 2x = 2 cos² x - 1
            = 2 (12/13)² - 1
            = 119 / 169