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-   -   ((sin(x)+sin(3x))/(2sin(2x)))=cos(x) (https://www.askmehelpdesk.com/showthread.php?t=706446)

  • Oct 2, 2012, 03:13 PM
    Squier93
    ((sin(x)+sin(3x))/(2sin(2x)))=cos(x)
    ((sin(x)+sin(3x))/(2sin(2x)))=cos(x)
  • Oct 3, 2012, 08:13 AM
    ebaines
    Hint: to get started use the identity sin(a+b)=sin(a)cos(b)-sin(b)cos(a), where a = x and b = 2x. Then the idenity cos(2x) = 2cos^2x-1 and sin(2x)=2sin(x)cos(x). The rest is just manipulation.

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