Results 1 to 5 of 5

Math Help - high school trig hmwk question, desperate help needed =[

  1. #1
    Newbie
    Joined
    Nov 2007
    Posts
    2

    high school trig hmwk question, desperate help needed =[

    Hello, here is the question:

    express sin2(theta) and cos2(theta) in terms of tan(theta). We have only learned compound and double angles so far, so I assume we are supposed to work with those, help is greatly appreciated =S
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Nov 2007
    Posts
    21
    do you mean cos^2(\theta) or cos(2\theta)??
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2007
    Posts
    2
    , sry about that
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,054
    Thanks
    368
    Awards
    1
    Quote Originally Posted by Morinphen View Post
    Hello, here is the question:

    express sin2(theta) and cos2(theta) in terms of tan(theta). We have only learned compound and double angles so far, so I assume we are supposed to work with those, help is greatly appreciated =S
    sin(2 \theta) = 2~sin(\theta)~cos(\theta)

    = 2~sin(\theta)~cos(\theta) \cdot \frac{cos(\theta)}{cos(\theta)}

    = 2 \frac{sin(\theta)}{cos(\theta)}cos^2(\theta)

    = 2~tan(\theta)~cos^2(\theta)

    Something like that? If you have an example of what your instructor is looking for it would be helpful.

    -Dan
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Math Engineering Student
    Krizalid's Avatar
    Joined
    Mar 2007
    From
    Santiago, Chile
    Posts
    3,654
    Thanks
    13
    Quote Originally Posted by topsquark View Post
    = 2~tan(\theta)~cos^2(\theta)
    Sure. Now from \frac{1}<br />
{{\cos ^2 \theta }} = 1 + \tan ^2 \theta \implies \cos ^2 \theta = \frac{1}<br />
{{1 + \tan ^2 \theta }}.

    So \sin 2\theta = \frac{{2\tan \theta }}<br />
{{1 + \tan ^2 \theta }}.

    I think he means that.

    --

    Ohhh, nice formula, could be helpful to integrate someday
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. High School Trig
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 17th 2010, 05:54 PM
  2. high school algebra question
    Posted in the Algebra Forum
    Replies: 8
    Last Post: March 10th 2010, 06:59 AM
  3. Replies: 1
    Last Post: November 30th 2008, 11:00 AM
  4. Grade 11 High School Circles Question
    Posted in the Geometry Forum
    Replies: 2
    Last Post: November 30th 2008, 09:35 AM
  5. high school
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 29th 2007, 08:49 PM

Search Tags


/mathhelpforum @mathhelpforum