sin (x + y) / sin x sin y = cot x + cot y

Bab Trigonometri
Matematika SMA Kelas X

(sin (x + y)) / (sin x sin y)
= (sin x cos y + cos x sin y)/(sin x sin y)
= (sin x cos y)/(sin x sin y) + (cos x sin y)/(sin x sin y)
= (cos y)/sin y + (cos x)/sin x
= cot y + cot x
= cot x + cot y

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