Sin A = 1 per 2 ,Cos B = √3 per 2

SIN A=1/2,COS A=akar3/2 ------>phytagorasCOS B=akar 3/2,SIN A=1/2------>phytagorasMaka COS (A-B)=COS A.COS B+SIN A.SIN B =akar3/2.akar3/2+1/2.1/2 =3/4+1/4 =4/4=1

"maaf kalo salah"