Results 1 to 2 of 2

Math Help - trig identity

  1. #1
    Newbie
    Joined
    Mar 2009
    Posts
    11

    Exclamation trig identity

    hey all this one question keeps bugging me if you could help thanks so much!
    if it is an identity prove it.
    (sinX+cosx)^2=1

    if i expand it it becomes
    sinx^2+cosx^2+2sinxcosx=1

    if i chose to changd sinx^2 to 1-cos^2 it becomes

    (1-cosx^2)+cosx^2+sinxcosx=1
    so it simplifies to
    1+sinxcosx=1
    I cant seem to go anywhere from there....if im on the right track please let me know! or is it just not an identity?
    THANKS!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by amanda0603 View Post
    hey all this one question keeps bugging me if you could help thanks so much!
    if it is an identity prove it.
    (sinX+cosx)^2=1

    if i expand it it becomes
    sinx^2+cosx^2+2sinxcosx=1

    if i chose to changd sinx^2 to 1-cos^2 it becomes

    (1-cosx^2)+cosx^2+sinxcosx=1
    so it simplifies to
    1+sinxcosx=1
    I cant seem to go anywhere from there....if im on the right track please let me know! or is it just not an identity?
    THANKS!
    so in other words, you have 1 = 1 + something

    and the something is not always 0. does that seem like an identity?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. trig identity help...
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: May 17th 2011, 09:43 AM
  2. Another trig identity
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: February 14th 2011, 04:54 PM
  3. Trig Identity
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: April 18th 2010, 05:43 PM
  4. Trig identity
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: March 9th 2010, 11:39 PM
  5. Odd Trig Identity
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: August 27th 2008, 08:06 PM

Search Tags


/mathhelpforum @mathhelpforum