View source for Relationship between cot and coth

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<strong>[[Relationship between cot and coth|Theorem]]:</strong> The following formula holds:
$$\cot(z)=i\coth(iz),$$
where $\cot$ denotes the [[cotangent]] and $\coth$ denotes the [[coth|hyperbolic cotangent]].
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<strong>Proof:</strong> █ 
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