Results 1 to 3 of 3

Math Help - Hint to proof this identity

  1. #1
    Junior Member
    Joined
    Nov 2009
    Posts
    58

    Hint to proof this identity

    Hi,

    Can anyone give me a hint/tip to get started with this question. I've been at it for an hour and just get a mish mash of sin and cos:

    Prove:

    <br />
\frac{cos(A)}{1 - tan(A)} + \frac{sin(A)}{1-cot(A)} = sin(A) + sin(A)<br />

    Thank you
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Amer's Avatar
    Joined
    May 2009
    From
    Jordan
    Posts
    1,093
    Quote Originally Posted by aceband View Post
    Hi,

    Can anyone give me a hint/tip to get started with this question. I've been at it for an hour and just get a mish mash of sin and cos:

    Prove:

    <br />
\frac{cos(A)}{1 - tan(A)} + \frac{sin(A)}{1-cot(A)} = sin(A) + sin(A)<br />

    Thank you
    correction
    you mean you want to prove this right ??

    \frac{cos(A)}{1 - tan(A)} + \frac{sin(A)}{1-cot(A)} = cos(A) + sin(A)

    to prove it first you know that

    \tan A = \frac{\sin A }{\cos A }

    \cot A = \frac{\cos A}{\sin A }

    1- \frac{\sin A }{\cos A } = \frac{\cos A - \sin A }{\cos A }

    make the same thing to the other denominator
    simplify you will have to fraction have the same denominator
    use
    (a^2 - b^2 ) = (a-b)(a+b)

    something will cancel then you will get the answer
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Nov 2009
    Posts
    58
    Thank you!!

    Also a million thanks Sorban, i can't thank you in a private message yet because my post count isn't high enough so i'm doing it here
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Integral of x.arctan(x) with hint with hint
    Posted in the Calculus Forum
    Replies: 3
    Last Post: May 22nd 2010, 06:57 AM
  2. Help on Hint
    Posted in the Differential Geometry Forum
    Replies: 2
    Last Post: February 21st 2010, 07:57 PM
  3. Proof by Induction (Urgent hint required)
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: November 25th 2008, 06:14 AM
  4. Inverse Isometry Proof Hint Help
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: April 7th 2008, 12:50 PM
  5. Induction hint
    Posted in the Advanced Algebra Forum
    Replies: 0
    Last Post: February 6th 2008, 07:00 PM

Search Tags


/mathhelpforum @mathhelpforum