Question

Срочно 15 баллов алгебра

Answer 1

$cosfrac{5pi}{12}-cosfrac{3pi}{12}=cos75^circ -cos45^circ =cos(45^circ+30^circ)-cos45^circ =\\=cos45^circ cdot cos30^circ -sin45^circ cdot sin30^circ -frac{sqrt2}{2}=frac{sqrt2}{2}cdot frac{sqrt3}{2}-frac{sqrt2}{2}cdot frac{1}{2}-frac{sqrt2}{2}=\\=frac{sqrt6-sqrt2-2sqrt2}{4}=frac{sqrt6-3sqrt2}{4}=frac{sqrt6, (1-sqrt3)}{4}$