Question

Diketahui nilai sin A sin B = 2/5 dan (A+B) = phi/2
nilai cos (A-B).?

Answer 1

- 2 sin A sin B = cos (A + B) - cos (A - B)
-2 (2/5) = cos (π/2) - cos (A - B)
-4/5 = 0 - cos (A - B)
Cos (A - B) = 4/5

Answer 2

Sin a. Sin b = 2/5
A+b = phi/2

2.Sin a.sin b = cos(a-b) - cos(a+b)
2.2/5 = cos(a-b) - cos(phi/2)
4/5 = cos (a-b) - 0
Cos(a-b) = 4/5