Results 1 to 4 of 4

Math Help - [SOLVED] trig question

  1. #1
    Junior Member
    Joined
    Oct 2008
    Posts
    50

    [SOLVED] trig question

    so had my AS core 1 exam today - dont think i did very well, bugger. anyway the question is...

    You are given that tanA=\frac{1}{2} and the angle A is acute. show without using a calculator that cos^2A=\frac{4}{5}

    Please explain thoroughly

    ta
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261

    Re :

    Quote Originally Posted by coyoteflare View Post
    so had my AS core 1 exam today - dont think i did very well, bugger. anyway the question is...

    You are given that tanA=\frac{1}{2} and the angle A is acute. show without using a calculator that cos^2A=\frac{4}{5}

    Please explain thoroughly

    ta

    Note that tan A is in the first quadrant . Draw a triangle ..

    From there you will be able to find that cos A = \frac{2}{\sqrt 5}

    Squarring it , you should get the results ...
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Oct 2008
    Posts
    50

    sorry to be...

    ....stupid but i dont understand this as of yet and require it to be explained more if at al possible, the book is just confusing me!

    ta
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261

    Re :

    Quote Originally Posted by coyoteflare View Post
    ....stupid but i dont understand this as of yet and require it to be explained more if at al possible, the book is just confusing me!

    ta

    Alright , it is ok . Firstly , do u know that when you are given the value of a trigo function , ie
    tanA=\frac{1}{2}
    you can draw a triangle and find cos A and sin A as well ?
    If u do , well , the question tells us that A is an acute ( smaller than 90 ) , so we know that tan A is in the first quadrant and everything is positive here .

    Note that (cos A)^2=cos^2A
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Need help with Trig Sum Formulas Question
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: March 27th 2010, 05:10 PM
  2. [SOLVED] another trig limit question
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: October 19th 2009, 10:36 PM
  3. [SOLVED] trig question
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: June 5th 2009, 04:43 AM
  4. [SOLVED] Trig. and Sin Wave Question
    Posted in the Math Topics Forum
    Replies: 5
    Last Post: May 18th 2008, 11:20 AM
  5. [SOLVED] Trig Question
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: October 14th 2007, 10:50 PM

Search Tags


/mathhelpforum @mathhelpforum