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Why is this equation equal to another equation?

  1. May 29, 2010 #1
    x = (2vsin(theta)cos(theta))/g = (vsin2(theta))/g

    v = null velocity

    x = distance

    g = gravity

    How is the first equation equal to the second one?
    How the sin2(theta) come to be and where did the cos(theta) go?
  2. jcsd
  3. May 29, 2010 #2


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    Science Advisor

    Trigonometric identity:

    [tex]2 \sin (\theta) \cos (\theta) = \sin (2 \theta)[/tex]
  4. May 29, 2010 #3
    thank you
  5. May 29, 2010 #4
    Or more generally, sin(A+B)=sin(A)cos(B)+cos(A)sin(B).
    Also handy to know: cos(A+B)=cos(A)cos(B)-sin(A)sin(B).
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