Question

sina/
1-cosa
= 1+cosa/
sina​

Answer 1

$\frac{sin(a)}{1-cos(a)} = \frac{1+cos(a)}{sin(a)} \\\frac{sin(a)}{1-cos(a)} = \frac{1+cos(a)}{sin(a)}, a\neq k\pi , k e Z\\sin(a)^2=(1+cos(a))*(1-cos(a))\\sin(a)^2=1-cos(a)^2\\sin(a)^2=sin(a)^2\\a e R, a\neq k\pi , k e Z\\a e R (k\pi , k e Z)$