Results 1 to 3 of 3

Math Help - Trig Identity Problem

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    21

    Trig Identity Problem

    I'm having trouble with this trig identity:

    \frac{cosA}{1-tanA}+\frac{sinA}{1-cotA}\equiv sinA + cosA

    It seems I'll have to add the two fractions on the LHS to get the RHS.

    Adding the fractions gave me:

    \frac{cosA+sinA-cosAcotA-sinAtanA}{2-cotA-tanA}

    After that I don't know what I can do to simplify it to get the RHS. Any hints/solutions would be welcome. Thanks in advance.
    Last edited by tleave2000; April 18th 2009 at 03:36 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Mar 2007
    Posts
    1,240

    Talking

    Try converting everything on the left-hand side to sines and cosines.

    The first fraction should simplify as (cos^2(A))/(cos(A) - sin(A)).

    The second fraction should simplify as (sin^2(A))/(sin(A) - cos(A)).

    Note that sin(A) - cos(A) = -[cos(A) - sin(A)], and combine the fractions.

    Factor the difference of squares in the numerator. Cancel the common factor.

    What are you left with? :wink:
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2009
    Posts
    21
    Awesome, thanks a lot!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Identity Problem
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: September 7th 2011, 02:08 PM
  2. Another Trig Identity problem.
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: November 28th 2010, 08:53 PM
  3. Trig identity problem
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: December 18th 2008, 08:23 PM
  4. Trig identity problem
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: November 9th 2007, 09:37 PM
  5. Help with a Trig Identity Problem
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: June 30th 2007, 08:22 AM

Search Tags


/mathhelpforum @mathhelpforum