Diketahui tan a = 3/4 , tan b =8/15 a dan b sudut lancip. Nilai sin a cos b - cos a sin b adalah... A. 13/85 B. 36/85 C. 60/85 D. 77/85 E. 84/85 Pakai caranya y

trigonometri
tanA = 3/4= y/x  --> triple pitagoras x,y,r = 3,4,5
sin A = y/r = 3/5
cos A = x/r = 4/5

tanB = 8/15 = y/x ---> triple pitagoras  x,y,r =15,8 17
sinB = y/r =8/17
cos B = x/r = 15/17

sin A cos B - cos A sin B = (3/5)(15/17) - (4/5)(8/17) = 45/85-32/85
sin A cos B - cos A sin B = 13/85