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How do I factorise this radian equation?

  1. Jul 10, 2012 #1
    Factorise:

    2sinx cosx - 4sin^3x cosx

    I don't want just a simple explanation with an answer, I need a full explanation of every mathematical step.
     
  2. jcsd
  3. Jul 10, 2012 #2

    jedishrfu

    Staff: Mentor

    2 * S * C - 4 * S * S * S * C

    cant you see the common factors in each term?

    we cant help you if you dont show any work.
     
  4. Jul 10, 2012 #3

    jedishrfu

    Staff: Mentor

    is this a repeat post of the same problem?

    This was previously posted in another thread!
     
    Last edited: Jul 10, 2012
  5. Jul 10, 2012 #4

    eumyang

    User Avatar
    Homework Helper

    How's your algebra skills? If you can factorize this algebraic expression:
    2xy - 4x3y
    ... then you should be able to factorize the original problem in a similar way.

    Sorry, no can do. If this is homework, then giving solutions would be against the forum rules.
     
  6. Jul 10, 2012 #5

    arildno

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    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    You simply MUST provide some intial steps on your own (you DO have that, right?)
    THEN, we can help you along with some more!

    While your expression can most elegantly be expressed strictly in terms of a single sine function, with amplitude one half, you need to show some willingness to get there at least some part of the way.
     
    Last edited: Jul 10, 2012
  7. Jul 11, 2012 #6
    Your steps are:

    1. Call sin(x)=a, cos(x)=b and rewrite the expression.
    2. Factor the expression with respect to a and b. (You know how to do that, right?)
    3. Substitute the trigonometric functions back.
    4. Write down the trigonometric identities you know.
    5. If you still can't see the solution, please reply (show some working.)
     
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