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Grade 11Trigonometry

If A+B+C =pie,then prove that ∑(tanA÷tanBtanC) = ∑(tanA) -2∑(cotA).

Profile image of kartikay kala
7 Years agoGrade 11
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1 Answer

Profile image of Saurabh Koranglekar
ApprovedApproved Tutor Answer7 Years ago
A+B+C = 180 ;

A+B = 180 – C ;

/* take tangent on both sides and simplifiy

Tan A + Tan B + Tan C = (Tan A)*(Tan B)*(Tan C)

take LCM of LHS in expanded form */

(Tan 2A +Tan2B+Tan2C) ./ ((Tan A)*(Tan B)*(Tan C))

simplify using (a^2 + b^2 + c^2) = (a+b+c)^2 – 2(ab + bc + ca);

you will get RHS