Question

вычислите 1) cos^2 15-sin^2 15

2) (cos15+sin15)^2

Answer 1

1) cos^2 15-sin^2 15=cos30=корень(3)/2

2)(cos15+sin15)^2=cos^2 15+2cos15*sin 15+sin^2 15=1+sin30=1+1/2=3/2