Re: Parametric Solving Question From 14 Year Old

*To*: mathgroup at smc.vnet.net*Subject*: [mg23519] Re: [mg23507] Parametric Solving Question From 14 Year Old*From*: Wagner Truppel <wtruppel at uci.edu>*Date*: Tue, 16 May 2000 22:29:52 -0400 (EDT)*References*: <200005160644.CAA17458@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Alan, I don't have access to Mathematica right now, so I'm going to answer this from memory. I think you want to use the function Solve[], or its numerical analog, NSolve[]. Something along the lines of Solve[ { x == 15*t*Cos[60*Degree], y == 15*t*Sin[60*Degree]-9.80665/2*t^2, y == 0 }, {x, t} ] which tells Mathematica to solve for the variables x and t. Incidentally, I suspect you meant 60 degrees, so it's important to have the Degrees constant inside the trig functions, because Sin[] and Cos[] assume their arguments to be in radians. Actually, I'm not sure now whether its correct name is Degree or Degrees. Hope this helps. Wagner At 2:44 AM -0400 on 5/16/00, Alan wrote: >Hello! > I am 14 and am wondering how to solve parametric equations directly >without graphing in Mathematica? I am figuring out when a projectile in >motion hits the ground only due to the even force of gravity acting upon >it. The parametric equation is: > >x(t)=15*t*Cos[60] >y(t)=15*t*Sin[60]-9.80665/2*t^2 > >I want to find the value x(t) and t when y(t)=0. > > Thank you, > Alan

**References**:**Parametric Solving Question From 14 Year Old***From:*Alan <alana@mac.com>