How do you prove $1/(1-cosA) + 1/(1+cosA)= 2+2cot^2A$ ?

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Answer 1 · 2015-04-30T17:07:46

Starting with the LHS, the sum would be

$(1+cos A +1 -cos A)/((1+cosA)(1-cosA))$

= $2/(1-cos^2A)$

= $2/sin^2A$

= $2csc^2A$

= $2(1+cot^2A)$

= $2+2cot^2A$

How do you prove 1/(1-cosA) + 1/(1+cosA)= 2+2cot^2A1/(1-cosA) + 1/(1+cosA)= 2+2cot^2A?