Derivative of Cotangent of Function
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Theorem
Let $u$ be a differentiable real function of $x$.
Then:
- $\map {\dfrac \d {\d x} } {\cot u} = -\csc^2 u \dfrac {\d u} {\d x}$
where $\cot$ is the cotangent function and $\csc$ is the cosecant function.
Proof
\(\ds \map {\frac \d {\d x} } {\cot u}\) | \(=\) | \(\ds \map {\frac \d {\d u} } {\cot u} \frac {\d u} {\d x}\) | Chain Rule for Derivatives | |||||||||||
\(\ds \) | \(=\) | \(\ds -\csc^2 u \frac {\d u} {\d x}\) | Derivative of Cotangent Function |
$\blacksquare$
Also see
Sources
- 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 13$: Derivatives of Trigonometric and Inverse Trigonometric Functions: $13.17$
- 1974: Murray R. Spiegel: Theory and Problems of Advanced Calculus (SI ed.) ... (previous) ... (next): Chapter $4$. Derivatives: Derivatives of Special Functions: $6$