# Projectile Motion.

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I know this gets asked a lot based on the amount of post I found searching for the answer but I need help with understanding some of what I found. I'm trying to have a stationary object fire at another object that has a constant velocity. However I don't have the aim or the time at which the stationary object's bullet hits the moving object. Basically this forum post is exactly what I'm attempting to do: http://www.gamedev.net/community/forums/topic.asp?topic_id=453829&whichpage=1� On the third post the guy goes over the equation I need to solve the problem, however when he gets to here:
Quote:
 Herein only t is unknown, and the whole formula is a quadratic equation in t. One can solve any quadratic equation of the form f(t) := t2 + c1 * t + c0 = 0 by the so-called "pq-formula" (well, it is called so in Germany), yielding in ta = - c1 / 2 + sqrt( c1^2 / 4 - c0 ) tb = - c1 / 2 - sqrt( c1^2 / 4 - c0 )
I get lost as I don't know where he got the c1 or c0. If someone could explain that to me where he got that, I'd greatly be appreciative.

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c1 means "whatever is multiplying t in the equation above" and c0 means "whatever is not multiplying t in the equation above".

If you need another explanation, I posted code and an explanation in this other thread: http://www.gamedev.net/community/forums/topic.asp?topic_id=401165

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