"Use the double argument property, \(\displaystyle cos 2x = 1 - 2 sin2x\) to express cos 60° in terms of sin 30°."

My response:

\(\displaystyle x=30°

cos(2*30°)=1-2sin^2(30°)

cos(60°)=1-2sin^2(30°)

(cos(60°)-1)/-2)=sin^2(30°)

0.25=sin^2(30°)

0.5=sin(30°)\)