cos75 - cos15 = cos(60+15) - cos15 = cos60cos15 - sin60sin15 - cos15 = (1/2)(√3/2) - (√3/2)(√3/2) - (√3/2) = (√3/4) - (3/4) - (√3/2) = -1/4 - √3/2.
Таким образом, cos75 - cos15 равно -1/4 - √3/2.
cos75 - cos15 = cos(60+15) - cos15 = cos60cos15 - sin60sin15 - cos15 = (1/2)(√3/2) - (√3/2)(√3/2) - (√3/2) = (√3/4) - (3/4) - (√3/2) = -1/4 - √3/2.
Таким образом, cos75 - cos15 равно -1/4 - √3/2.