Question

Найдите значение выражения
$\frac{12}{5sin( \frac{23 \pi }{4} )cos( \frac{21 \pi }{4} )}$

Answer 1

sin(23π/4)=sin(24π/4-π/4=sin(-π/4)=-sin(π/4)=-(√2)/2
cos(21π/4)=cos(24π/4-3π/4)=cos(-3π/4)=cos(3π/4)=-(√2)/2
5sin(23π/4)cos(21π/4)=5(-√2/2)²=5/2
12/(5/2)=24/5
Otvet:24/5