Question

cos(a+b), если cosa=0,6, sinb=-8/17, 3pi/2

Answer 1

сosa=0,6⇒sina=√(1-cos²a)=√(1-0,36)=√0,64=0,8
sinb=-8/17⇒cosb=√(1-sin²b)=√(1-64/289)=√(225/289)=15/17
cos(a+b)=cosacosb-sinasinb=0,6*15/17+8/17*0,8=45/85+32/85=77/85