cotx−cot2x =?

ব্যাখ্যা

cotx − cot2x = cos x/sin x − cos 2x/sin 2x = (sin 2x cos x − cos 2x sin x)/(sin x sin 2x) = sin (2x − x)/(sin x sin 2x) = sin x/(sin x·sin 2x) = 1/sin 2x = cosec 2x