Question

Como faz: 2 - 2 cos x= sen x . tg x

Answer 1

$2-2cos(x)=sen(x)tg(x)\\2-2cos(x)=sen(x)\frac{sen(x)}{cos(x)}\\\\2cos(x)-2cos^2(x)=sen^2(x)\\sen^2(x)+cos^2(x)+cos^2(x)=2cos(x)\\1+cos^2(x)=2cos(x)\\cos^2(x)-2cos(x)+1=[ cos(x) -1 ] ^2 =0\\\\cos(x)=1$