Question

$cos \alpha .tan \alpha = sin \alpha$

Answer 1

$\cos \alpha . \tan \alpha = \\ \cos \alpha . \sin \alpha \div \cos \alpha \\ \sin \alpha \\ = rhs$

Answer 2

cos
$cos \alpha . \sin\alpha \div \cos\alpha$

cos alpha will be cancelled so result will be
$\sin\alpha$