Question

Срочно 10 кл , только Д

Answer 1

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 p<a<3p/2 - 3 четверть sin a <0
cos(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