Sin^2 x/2 - cos^2 x/2 при x=2p/3

Question

Sin^2 x/2 - cos^2 x/2 при x=2p/3

Answer 1

sin^2(2p/3)/2)-cos^2(2p/3)/2)=sin^2 p/3 - cos^2 p/3= 1/4-3/4=-1/2

Answer 2

sin^2 x/2 - cos^2 x/2=-cos2*x/2=-cosx

-cos2пи/3=1/2