Hi prof Hwang
I modified project [b]*v^2 in a physlets formula for air resistance[/b] and come to my mind idea to add slider for control in angle(theta)
So i add slider position [b]up[/b] name is [b]theta[/b] and back to equation and typing it
vx=V*Math.cos(angle/90);
vy=V*Math.sin(angle/90);
After i back again to slider theta and add the following values in image gif that I'm attach
But I'm sure have wrong because when i drag slider theta to value less 40 simulation not work
I don't know why ??? ??? ???
Could you check prof what wrong i make
Thanks  :)
I attach also jar,,XML files of simulation