How to prove cot (A + B) = (cot A × cot B - 1) / (cot A + cot B)?

1.	How to prove cot (A + B) = (cot A × cot B - 1) / (cot A + cot B)?
Answer» Cot(A+B) =(cotAcotB-1) / (cotA+cotB) can be proved using trigonometric conversions from a cot function into cosine and sine function. We will make use of trigonometric identities to prove this result.

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