Question

Көмектесіңдерші тездетіп

Answer 1

sina=8/17
cosa=√1-sin²a)=√(1-64/289)=√(225/289)=15/17
cosb=4/5
sinb=√(1-cos²b)=√(1-16/25)=√(9/25)=3/5
cos(a+b)=cosacosb-sinasinb=15/17*4/5-8/17*3/5=60/85-24/85=36/85