Question

cos²112,5-sin²112,5 Очень срочно!​

Answer 1

$cos^2112.5^\circ -sin^2112.5^\circ =cos(2\cdot 112,5^\circ )=cos225^\circ =cos(180^\circ +45^\circ )=\\\\=-cos45^\circ =-\dfrac{\sqrt2}{2}$