Найдите sina+2cosa если tga/2=-2

Tga=2tg (a/2) / (1-tg² (a/2)) = 2 * (-2) / (1-4) = - 4/-3=4/3

cos²a=1; (1+tg²a) = 1: (1+16/9) = 1:25/9=9/25⇒cosa=-3/5 или cosa=3/5

1) cosa=-3/5⇒sina=√1-9/25=√16/25=4/5

sina+2cosa=4/5-2*3/5=4/5-6/5=-2/5

2) cosa=3/5⇒sina=-√1-9/25=-√16/25=-4/5

sina+2cosa=-4/5+2*3/5=-4/5+6/5=2/5