Results 1 to 4 of 4

Math Help - Trigonometry (cos)

  1. #1
    Member
    Joined
    Jun 2009
    Posts
    78

    Trigonometry (cos)

    Show cos \theta + cos (\theta + \alpha) + cos (\theta + 2\alpha) = (2 cos \alpha + 1) cos (\theta + \alpha)

    Answer:
    cos \theta + cos (\theta + \alpha) + cos (\theta + 2 \alpha)
    =[cos (\theta + 2 \alpha) + cos \theta] + cos (\theta + \alpha)
    =2 cos (\theta + \alpha) cos \alpha + cos (\theta + \alpha)
     =(2 cos \alpha + 1)cos (\theta + \alpha)

    My question is what happen between this step?
    =2 cos (\theta + \alpha) cos \alpha + cos (\theta + \alpha)
     =(2 cos \alpha + 1)cos (\theta + \alpha)
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jul 2009
    Posts
    593
    Thanks
    4
    cos(\theta + \alpha) was factored out.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Nov 2009
    Posts
    202
    please clarify your question. which step u didnot understand???
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Jun 2009
    Posts
    78
    Quote Originally Posted by Pulock2009 View Post
    please clarify your question. which step u didnot understand???
    I wanna know the formula between =2 cos (\theta + \alpha) cos \alpha + cos (\theta + \alpha)
     =(2 cos \alpha + 1)cos (\theta + \alpha) how were they factorised?
    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