Question

(sin195-cos195)^2 вычислить

Answer 1

$(sin195к-cos195к)^2=(sin(180к+15к)-cos(180к+15к))^2=$$=(-sin15к+cos15к)^2=(cos15к-sin15к)^2=$$=cos^215к+sin^215к-2cos15кsin15к=1-sin30к=1- frac{1}{2}= frac{1}{2}$