cot ( α ) = 1 tan ( α ) cot ( α ) = b a tan ( α ) = a b cot ( α ) tan ( α ) = b a ⋅ a b = 1 cot ( α ) tan ( α ) = 1 ⇓ cot ( α ) = 1 tan α {\displaystyle {\begin{aligned}\cot(\alpha )={\frac {1}{\tan(\alpha )}}\\\cot(\alpha )={\frac {b}{a}}\\\tan(\alpha )={\frac {a}{b}}\\\cot(\alpha )\tan(\alpha )={\frac {b}{a}}\cdot {\frac {a}{b}}=1\\\cot(\alpha )\tan(\alpha )=1\\\Downarrow \\\cot(\alpha )={\frac {1}{\tan \alpha }}\\\end{aligned}}}