(D@@2)(x)(t)=(-g/v)*sqrt(D(x)(t)^2+D(y)(t)^2)*D(x)(t)
(D@@2)(x)(t)=g-g/v*sqrt(D(x)(t)^2+D(y)(t)^2)*D(y)(t)
initial conditions
x(0)=0,y(0)=0,d(x)(0)=134,d(y)(0)=0
using rkf45
for time, 0-30
solve for x(t),y(t)
then i plan to plot the two and find the intersection
but i'm having trouble getting through the rkf45 to get my x(t) and y(t)

how do i solve a set of coupled differential equations like these for x(t) and y(t) eqn1 := (D,2)(x)(t) = -a*sqrt(D(x)(t)^2+D(y)(t)^2)*D(x)(t), eqn2 := (D,2)(y)(t) = g-a*sqrt(D(x)(t)^2+D(y)(t)^2)*D(y)(t)