Question

Tolong caranya & jawabannya. Makasih

Answer 1

Cos 2 A = 8/10 = 4/5
cos 2 A = 2 cos² A - 1 = 4/5
cos² A   =1/2 ( 4/5 + 1) = 9/10
cos A = √(9/10)= 3/10  √10

cos 2 A = 1 - 2sin² A 
4/5 = 1 - 2 sin² A
2 sin² A = 1 - 4/5 = 1/5
sin² A = 1/10
sin A = √(1/10) = 1/10 √10

tan A = sin A /cos A = (1/10 √10) / (3/10 √10) = 1/10 : 3/10= 1/3