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Homework Help: Proof - Projectile's Range

  1. Oct 11, 2008 #1
    1. The problem statement, all variables and given/known data

    Prove that a projectile launched at angle @ has the same horizontal range as one launched with the same speed at angle (90 - @).

    2. Relevant equations

    Obviously kinematics will be used =/

    3. The attempt at a solution

    I've been messing around with kinematics but haven't gotten anywhere. I also know that sin(90-@) = cos(@) . Help appreciated :]
  2. jcsd
  3. Oct 11, 2008 #2
    let the initial speed be V, and decomposite into V_y=Vsin@ and V_x=Vcos@. Now use this to first calculate the time the projectile is in the air and then the range of the projectile.
  4. Oct 11, 2008 #3
    I appreciate the help but when you decomposite the V wouldn't it be:

    V_y = sin(90-@)
    V_x = cos(@)
  5. Oct 11, 2008 #4
    uhm no, you said yourself that sin(90-@)=cos@, so that would give V_y=V_x :)
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