Results 1 to 2 of 2

Math Help - Trigonometry

  1. #1
    Junior Member
    Joined
    Jun 2008
    Posts
    40

    Trigonometry

    find the following:

    sin(15pi/4)

    cos(20pi/3)

    tan(-17pi/3)

    sin(-13pi/2)

    cos(19pi)

    Thanks for your help
    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 tim_mannire View Post
    find the following:

    sin(15pi/4)

    cos(20pi/3)

    tan(-17pi/3)

    sin(-13pi/2)

    cos(19pi)

    Thanks for your help
    \sin(2\pi + a) = \sin a

    this thing true for all trigonometry cos, tan, sec all

    \sin (\pi + a) = -\sin (a) true for sin and cos

    \tan (\pi +a) = \tan a

    can you prove what I wrote
    you should know that,

    \sin \frac{15\pi}{4} = \sin \left(3 + \frac{3}{4}\right)\pi = \sin \left(\pi + \frac{3\pi}{4}\right)=- \sin \frac{3\pi}{4} = - \left(\frac{-1}{\sqrt{2}}\right)

    \tan \frac{-17\pi}{3} = - \tan \frac{17\pi}{3} = -\tan \left(5 + \frac{2}{3}\right)\pi =  - \tan \left(1 + \frac{2}{3}\right)\pi = - - \tan \frac{2\pi}{3}= - \tan \frac{\pi}{3} = -\sqrt{3}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trigonometry to Memorize, and Trigonometry to Derive
    Posted in the Trigonometry Forum
    Replies: 9
    Last Post: August 21st 2013, 12:03 PM
  2. How To Do Trigonometry For This...?
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: January 10th 2009, 05:56 PM
  3. How To Do This Trigonometry
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: January 3rd 2009, 01:55 AM
  4. trigonometry
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: December 31st 2008, 08:06 PM
  5. Trigonometry
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: December 18th 2008, 04:40 PM

Search Tags


/mathhelpforum @mathhelpforum