Question

Buktikan bahwa: cot ( A + B ) = cot A cot B - 1 / cot A + cot B

Answer 1

Verified answer

Bab Trigonometri
Matematika SMA Kelas X

cot (A + B) = 1/(tan (A + B)
                  = 1 : ((tan A + tan B) / (1 - tan A . tan B))
                  = (1 - tan A tan B) / (tan A + tan B)
                  = (1 - 1/cot A . 1/cot B) / (1/cot A + 1/cot B)
                  = ((cot A . cot B - 1)/(cot A . cot B)) : (cot B + cot A)/(cot A . cot B)
                  = (cot A . cot B - 1) / (cot A + cot B)

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