Question

Diketahui sin A= 3/5 dan sec B= 13/12, dengan A sudut lancip dan B di kuadran III. nilai cos A dan cos B + sin A sin B =

Answer 1

Sin A = 3/5
cos A =√(1 - sin² A) = √(1- 9/25) = +_ 4/5
A di KDI --> cos A = 4/5

sec B = 13/12--> B diKD III
cos B = -12/13 --> sin B = +- 5/13
sin B = - 5/13

cos B + sin A sin B = - 12/13 + 3/5 (-5/13)= -12/13 - 3/13 = -15/13