Ask Your Question

# Revision history [back]

### desolve_system problem with exp()/e^

Hi!

I'm trying to solve ode system: x'=-2x+2y+e^t, y'=-2x+3y+3e^t

This is what I tried in Sage:

reset()

var('t')

x = function('x', t)

y = function('y', t)

dgl1 = x.diff(t) == -2 * x + 2 * y + exp(t)

dgl2 = y.diff(t) == -2 * x + 3 * y + 3 * exp(t)

dgls = [dgl1, dgl2]

aw = [0, 0, -1]

S = desolve_system(dgls, [x, y], aw)

But I always get this error:

Traceback (click to the left of this block for traceback)

...

TypeError: ECL says: Maxima asks: Is ?g9271-1 positive, negative, or zero?

If I remove the exp(t) it works fine, also if I replace the exp(t) with for example 2^t Sage gives me a solution. I already tried using e^t instead of exp(t) and tried some assumptions (assume(x >= 0), assume(t >= 0), etc.). Anyone got an idea what I'm doing wrong? Thanks in advance!

 2 retagged tmonteil 24333 ●27 ●176 ●447 http://wiki.sagemath.o...

### desolve_system problem with exp()/e^

Hi!

I'm trying to solve ode system: x'=-2x+2y+e^t, y'=-2x+3y+3e^t

This is what I tried in Sage:

reset()

var('t')

x = function('x', t)

y = function('y', t)

dgl1 = x.diff(t) == -2 * x + 2 * y + exp(t)

dgl2 = y.diff(t) == -2 * x + 3 * y + 3 * exp(t)

dgls = [dgl1, dgl2]

aw = [0, 0, -1]

S = desolve_system(dgls, [x, y], aw)

But I always get this error:

Traceback (click to the left of this block for traceback)

...

TypeError: ECL says: Maxima asks: Is ?g9271-1 positive, negative, or zero?

If I remove the exp(t) it works fine, also if I replace the exp(t) with for example 2^t Sage gives me a solution. I already tried using e^t instead of exp(t) and tried some assumptions (assume(x >= 0), assume(t >= 0), etc.). Anyone got an idea what I'm doing wrong? Thanks in advance!