Question
Mon September 21, 2009 By:

pls solve

Expert Reply
Tue November 24, 2009

we assume that   you want  to prove 2tan10+tan40=tan50

consider tan 50= tan (10+40) = (tan 10+tan 40)/(1-tan 10tan 40)

so tan 50-tan 50tan10tan40 = tan 10+tan 40

tan 50-cot40tan10tan40 = tan 10+tan 40

so tan 50=tan 10+tan 40+tan10 =2tan10+tan40

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