Diketahui alfa +beta =pi/2,sin alfa cos beta =2/3 dan sin (alfa-beta)=3a.Hitunglah nilai a

A + B = 90° ( 1 phi = 180°)
sin (A + B) = sin.90°
sin A.cos B + cos A.sin B = 1
2/3 + cos A.sin B = 1 (sin A.cos B = 2/3 didapat dari soal) -
cos A.sin B = 1 - 2/3 = 1/3
sin (A - B) = sin A.cos B - cos A.sin B
3a = 2/3 - 1/3
3a = 1/3
a = (1/3) /3
a = 1/9