نکته:   $\operatorname{Cos}2\alpha =2{{\operatorname{Cos}}^{2}}\alpha -1$ و $\operatorname{Sin}2\alpha =2\operatorname{Sin}\alpha \operatorname{Cos}\alpha $  با استفاده از نكته‌ی بالا داريم: $\frac{1+\operatorname{Cos}2\alpha }{\operatorname{Sin}2\alpha }=\frac{1+2{{\operatorname{Cos}}^{2}}\alpha -1}{2\operatorname{Sin}\alpha \operatorname{Cos}\alpha }=\frac{2{{\operatorname{Cos}}^{2}}\alpha }{2\operatorname{Sin}\alpha \operatorname{Cos}\alpha }=\frac{\operatorname{Cos}\alpha }{\operatorname{Sin}\alpha }=Cot\alpha $