sin a = 3/5 dan cos b = 5/13. (a dan b sudut lancip). berapakah nilai sin (a + b) =

jawab

sin A = 3/5
cos A = 4/5

cos B = 5/13
sin B = 12/13

sin (A + B)= sin A cos B + cos A sin B
= 3/5 (5/13) + 4/5 (12/13)
= (15/65)+ (48/65)
= 63/65