Question

sin^2a+ctg^2a+cos^2a=1/sin^2a

Answer 1

$Sin^{2}alpha+Ctg^{2}alpha+Cos^{2}alpha=(Sin^{2}alpha+Cos^{2}alpha)+frac{Cos^{2}alpha}{Sin^{2}alpha}=1+frac{Cos^{2}alpha}{Sin^{2}alpha}=frac{Sin^{2}alpha+Cos^{2}alpha}{Sin^{2} alpha }=frac{1}{Sin^{2} alpha }\frac{1}{Sin^{2}alpha}=frac{1}{Sin^{2}alpha}$