Question

(sina+sinb)^2+(cosa+cosb)^2=4cos^2 a-b/
Pleeeeeeease help me......

Answer 1

(sina+sinb)^2+(cosa+cosb)^2=sina^2+2sina*sinb+sinb^2+cosa^2+2cosa*cosb+cosb^2==1+1+2sina*sinb+2cosa*cosb=2+2cos(a-b)=2(1+cos(a-b))

Answer 2

Огромное спасибо!