Question

Jika 90° < x > 180° dan tan x = -a, maka (sin x + cos x) ² =

Answer 1

90 < x < 180 (kuadran II)
tan x = - a (depan/samping)
sin x = a/√(a² + 1)
cos x = - 1/√(a² + 1)  (cos di kuadran II bernilai negatif)

(sin x + cos x)² = (a/√(a² + 1) - 1/√(a² + 1))
                       = ((a - 1)/(√(a² + 1))
                       = (a² - 2a + 1)/(a² + 1)