Math Problem Statement

tanA/1-cotA + cotA/1-tanA = 1+ tanA + cotA

Solution

We are given the equation to prove:

tanA1cotA+cotA1tanA=1+tanA+cotA\frac{\tan A}{1 - \cot A} + \frac{\cot A}{1 - \tan A} = 1 + \tan A + \cot A

Steps to Prove the Identity:

  1. Convert cotA\cot A to tanA\tan A: We know that cotA=1tanA\cot A = \frac{1}{\tan A}. Substituting this into the equation:

    tanA11tanA+1tanA1tanA\frac{\tan A}{1 - \frac{1}{\tan A}} + \frac{\frac{1}{\tan A}}{1 - \tan A}

  2. Simplify the terms: Simplify the denominator in the first fraction:

    tanAtanA1tanA=tanAtanAtanA1=tan2AtanA1\frac{\tan A}{\frac{\tan A - 1}{\tan A}} = \frac{\tan A \cdot \tan A}{\tan A - 1} = \frac{\tan^2 A}{\tan A - 1}

    Simplify the second fraction:

    1tanA1tanA=1tanA(1tanA)\frac{\frac{1}{\tan A}}{1 - \tan A} = \frac{1}{\tan A (1 - \tan A)}

    Now the equation becomes:

    tan2AtanA1+1tanA(1tanA)\frac{\tan^2 A}{\tan A - 1} + \frac{1}{\tan A (1 - \tan A)}

  3. Get common denominators: The common denominator of these two fractions will be (tanA1)(1tanA)(\tan A - 1)(1 - \tan A). So we rewrite the fractions:

    tan2AtanA1+11tanA\frac{\tan^2 A}{\tan A - 1} + \frac{1}{1 - \tan A}

  4. Combine fractions: Add the two fractions with the common denominator:

    tan2A+1(1tanA)(tanA1)\frac{\tan^2 A + 1}{(1 - \tan A)(\tan A - 1)}

    Since (1tanA)(tanA1)=(tanA1)2(1 - \tan A)(\tan A - 1) = -(\tan A - 1)^2, the equation becomes:

    tan2A+1(tanA1)2\frac{\tan^2 A + 1}{-(\tan A - 1)^2}

  5. Use trigonometric identities: Now use the identity tan2A+1=sec2A\tan^2 A + 1 = \sec^2 A. So the expression simplifies to:

    sec2A(tanA1)2\frac{\sec^2 A}{-(\tan A - 1)^2}

    This should simplify further to give us the right-hand side, but it appears there's a sign issue in how we've proceeded. Let me review the algebra and approach it differently