Question

ДАЮ 25!!!

Умоляю, решите, очень срочно!!!

Answer 1

Докажите 
$frac{cosalpha}{1-sin alpha} -frac{cosalpha}{1+sin alpha}=2tg alpha$
Доказательство
$frac{cosalpha}{1-sin alpha} -frac{cosalpha}{1+sin alpha}= frac{cos alpha (1+sin alpha )-cos alpha (1-sin alpha )}{(1-sin alpha )(1+sin alpha )} = frac{cos alpha (1+sin alpha -1+sin alpha )}{1-sin^2 alpha }=$$frac{cos alpha* 2sin alpha}{cos^2 alpha }= frac{2sin alpha}{cos alpha }=2tg alpha$