Question

Выражение: 1 - sin²α/1 - cos²α : 1+ ctg²α/1+tg²α =

Answer 1

$\frac{1-Sin^{2}\alpha}{1-Cos^{2}\alpha}:\frac{1+Ctg^{2}\alpha}{1+tg^{2}\alpha}=\frac{Cos^{2}\alpha}{Sin^{2}\alpha}:\frac{\frac{1}{Sin^{2}\alpha}}{\frac{1}{Cos^{2}\alpha }}=\frac{Cos^{2}\alpha}{Sin^{2}\alpha}:\frac{Cos^{2}\alpha}{Sin^{2}\alpha} =1$

При решении были использованы формулы :

$Sin^{2}\alpha+Cos^{2}\alpha =1\\\\Sin^{2}\alpha =1-Cos^{2}\alpha\\\\Cos^{2}\alpha =1-Sin^{2}\alpha\\\\1+tg^{2}\alpha =\frac{1}{Cos^{2}\alpha}\\\\1+Ctg^{2}\alpha=\frac{1}{Sin^{2} \alpha }$