Cotangent of Right Angle

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Theorem

$\cot 90^\circ = \cot \dfrac \pi 2 = 0$

where $\cot$ denotes cotangent.


Proof

\(\displaystyle \cot 90^\circ\) \(=\) \(\displaystyle \frac {\cos 90^\circ} {\sin 90^\circ}\) Cotangent is Cosine divided by Sine
\(\displaystyle \) \(=\) \(\displaystyle \frac 0 1\) Cosine of Right Angle and Sine of Right Angle
\(\displaystyle \) \(=\) \(\displaystyle 0\)

$\blacksquare$


Also see


Sources