Question

(cosx+cosy)^2+(sinx-siny)^2=4cos^2=x+y÷2

Answer 1

I hope this helps you.

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Answer 2

(cosx+cosy)2+(sinx+siny)2

cos2x+cos2y+2cosxcosy+sin2x+sin2y+2sinxsiny

2(1+cosxcosy+sinx siny)

2(1+cos(x−y))

2×2cos²(x−y/2)

4cos2(x−y/2)
$|proved|$

Hope that this answer will help you ❤️❤️❤️