Question

Упростите sin a/2sin^2 a/2

Answer 1

$frac{sina}{2sin^2( frac{a}{2}) }= frac{sin(2* frac{a}{2}) }{2sin^2( frac{a}{2})}= frac{2sin frac{a}{2}cos frac{a}{2}}{2sin^2( frac{a}{2})} = frac{cos frac{a}{2}}{sin frac{a}{2}} =ctg frac{a}{2}$