If π < 2θ < 3π2 then √2+√2+2cos4θ is equal to
-2sinθ
2cosθ
2sinθ
√2+√2(1+cos4θ) = √2+2|cos2θ|
= √2(1−cos2θ) = 2|sinθ| = 2sinθ as π2 < θ < 3π4