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C3 help

  1. Jan 2, 2008 #1

    Could someone please help me with the following C3 question? I would really appreciate any help as I am completely stuck at the moment.

    Find, in terms of pi, the solutions of the equation sin5x + sin x = 0 for x in the interval 0 >= x > pi.

    I wrote down that sin(3x + 2x) + sin x = 0 and that sin3xcos2x + cos3xsin2x + sin x = 0 but I am not sure where to go from here or if this is even the correct method.

    Thank you.

    Last edited: Jan 2, 2008
  2. jcsd
  3. Jan 2, 2008 #2
    You have to use the Sin C + sin D forumla. If you don't know how to derive it add sin(x+y) and sin(x-y) together, call x+y= A and x-y= B, then solve for x and y and resubst to get:

    sin A + sin B= 2sin ((A+B)/2) x cos ((A-B)/2)

    That should help you.

    Your interval is 0 >= x > p which reads as 0 is greater than x and x is greater than pi, so 0 is greater than pi?
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