Which of the following is a double angle identity?sinθ=cos(π2−θ)sine theta is equal to cosine of open paren pi over 2 minus theta close parencos(2θ)=cos2θ−sin2θcosine of 2 theta is equal to cosine squared theta minus sine squared thetasin(−θ)=−sinθsine of negative theta is equal to negative sine thetacos2θ+sin2θ=1
