Hello, I need make procedure for following instance. I want enter only: v, phi, sirka, k

Thank you...

restart:

with(DEtools):

v := 4;

phi := 1/3*Pi;

sirka := 10;

k := .2;

eq1 := diff(x(t), t) = v*cos(phi):

eq2 := diff(y(t), t) = -v*sin(phi)+k*x(t)*(sirka-x(t)):

sys := [eq1, eq2]:

Good Morning, I´m sorry, but be unable to write English. I have following problem:

I need draw curve.

This is all right:

with(DEtools); with(plots):

r1 := diff(x(t), t) = (x(t)-y(t))/sqrt(x(t)^2+y(t)^2);

r2 := diff(y(t), t) = (x(t)+y(t))/sqrt(x(t)^2+y(t)^2);

sys := {r1, r2};

DEplot(sys, {x(t), y(t)}, t = 0 .. 1, x = -1 .. 1, y = -1 .. 1, stepsize = 0.5);