Results 1 to 2 of 2

Math Help - Trig Identities

  1. #1
    Senior Member polymerase's Avatar
    Joined
    May 2007
    From
    Sydney
    Posts
    267

    Trig Identities

    In a question I was given, in order to solve it, I needed to simplify \sin\left(\frac{3}{2}x\right)\cos\left(\frac{3}{2}  x\right) to \frac{1}{2}\sin 3x. This is "obvious" related to the identity 2\sin x \cos x = \sin 2x.?

    So my question is, what's the rule (if any) to simplify these forms of expressions?

    Lets use the example of \sin\left(\frac{3}{\sqrt{2}}x\right)\cos\left(\fra  c{3}{\sqrt{2}}x\right) or \sin\left(\frac{4}{5}x\right)\cos\left(\frac{4}{5}  x\right), what do those simplify to?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    This is "obvious" related to the identity
    Yes

    Quote Originally Posted by polymerase View Post
    \sin\left(\frac{3}{\sqrt{2}}x\right)\cos\left(\fra  c{3}{\sqrt{2}}x\right)
    It depends on what purpose, sometimes, it's easier not to simplify.

    =\frac{1}{2} \sin \left(2 \cdot \frac{3}{\sqrt{2}} x \right)=\frac{1}{2} \sin \left(3 \sqrt{2} \ x \right)

    Is it what you want ?


    or \sin\left(\frac{4}{5}x\right)\cos\left(\frac{4}{5}  x\right), what do those simplify to?
    =\frac 12 \sin \left(\frac{8}{5} x \right) ?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Identities
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 3rd 2009, 07:44 AM
  2. Trig identities
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: June 22nd 2009, 07:58 AM
  3. Trig Identities
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: November 9th 2008, 05:35 PM
  4. Trig Identities
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 7th 2008, 09:25 PM
  5. Trig Identities Help!!!!
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: April 14th 2008, 12:47 PM

Search Tags


/mathhelpforum @mathhelpforum