Question

(cos θ + cos θ)2 + (cos θ + cos θ)2

Answer 1

$\bf [cos(\theta)+cos(\theta)]^2+[cos(\theta)+cos(\theta)]^2\implies [2cos(\theta)]^2+[2cos(\theta)]^2 \\\\\\ 2^2[cos(\theta)]^2+2^2[cos(\theta)]^2\implies 4[cos(\theta)]^2+4[cos(\theta)]^2 \\\\\\ 8[cos(\theta)]^2\iff 8cos^2(\theta)$