Срочно 10 кл , только Д
Cos98*cos53 + sin98*sin53=0.5(cos151 + cos45)+0.5(cos45-cos151)=cos45=√2/2 sin56*cos26 - cos56*sin26=0.5(sin82 + sin30 - sin82 + sin30)=0.5 * 1=1/2 sin(8p/7)*cos(6p/7)+sin(6p/7)*cos(8p/7)=0.5(sin2p + sin2p/7 + sin2p -sin2p/7)=0.5 * 2sin2p = 0.5 * 0 = 0 cos3a*cos2a - sin2a*sin3a=0.5(cos5a + cosa - cosa + cos 5a)=cos5a cos(a+p/4) cosa=-3/5 pcos(a+p/4)=cosa*cosp/4-sina*sinp/4=-3/5 * √2/2 -√2/2 sina sin a =-√(1-9/25)=-4/5 -3/5 * √2/2 +√2/2 sina = -3√2/10 + 4√2/10=√2/10