Question

Дано sin a=-5/13, cos b=-12/13, найти sin(a+b)

Answer 1

sin (a+b)=sinacosb+sinbcosa
cos^2a=1-25/169=144/169
cosa=12/13
sinb=5/13
sin (a+b)=-5/13×5/13+12/13×(-12/13)=-25/169-144/169=-1