Question

Вычислить : cos²75°-sin²75°​

Answer 1

Ответ:

cos²75° - sin²75° = cos(2·75°) = cos150° = cos(180°-30°) = - cos30° = - √3/2.

Answer 2

Ответ:

$cos^275^\circ -sin^275^\circ =cos(2\cdot 75^\circ )=cos150^\circ =cos(180^\circ -30^\circ )=\\\\=-cos30^\circ =-\dfrac{\sqrt3}{2}$