1) cos 3a cos a – cos 7a cos 5a; 3) sin 4b cos - вопрос №649828713753435223 от nastakim68 17.11.2021 00:11

Question

Алгебра: 1) cos 3a cos a – cos 7a cos 5a; 3) sin 4b cos 3b – sin 5b cos 2b; 2) cos 3a cos a – sin 3a sin a; 4) sin 4b cos 3b – cos 4b sin 3b.

nastakim68 · Answer

11/2*cos2a+1/2*cos4a-1/2*cos2a-1/2*cos12a=1/2*(cos4a-cos12a)==1/2*2sin8asin4a=sin8asin4a21/2*cos2a+1/2*cos4a-1/2*cos2a+1/2*cos4a=cos4a31/2*sinb+1/2*sin7b-1/2*sin3b-1/2*sin7b=1/2*(sinb-sin7b)==1/2*2sin(-3b)cos4b=-sin3bcos4b4sin(4b-3b)=sinb...