Question

Упростите:
$\frac{1+cos 8a}{sin 8a}$

Answer 1

Ответ:

$\boxed{\ cos2x=2cos^2x-1\ \ \ \Rightarrow \ \ \ \ 1+cos2x=2cos^2x\ \ \ ,\ \ \ cos^2x=\dfrac{1+cos2x}{2}}\\\\\\\\\dfrac{1+cos8a}{sin8a}=\dfrac{2cos^24a}{2\, sin4a\cdot cos4a}=\dfrac{cos4a}{sin4a}=ctg4a$