<span>2+cos2x=2</span><span>sin</span><span>x</span>
-sin^2(x)+cos^2(x)+2=2 sin(x)
cos(2x)-2 sin(x)=-2
log5(1/5)-log1/2(2^2)=log5(5^-1)-log1/2((1/2)^-2)=-1+2=1