Question

Dik: sin α=1/2 cosβ=√3/2 β=sudut tumpul hitunglah cos (α-β)

Answer 1

Sin A = 1/2
cos A = √(1 - sin² A) = √(1-1/4) = √(3/4) = +_ 1/2 √3
A lancip --> cos A = 1/2 √3

B tumpul  --> cos B = -√(3/2) = -1/2 √3
sin B = √(1 - cos² B) = √(1 - 3/4) = √1/4 = 1/2

cos (A- B) = cos A cos B + sin A sin B
= (1/2 √3)(-1/2 √3) + (1/2)(1/2)
= - 3/4 + 1/4
= - 2/4
= - 1/2
..