# Laplace transform bug

jcfried shared this problem 6 years ago 1

If you look in the Algebra View, you'll see that you have defined

a(x) = sin(2x)²

so Laplace[sin(a*t),t] isn't doing what you expect 1

Michael, thanks. While i cannot see the entry in algebra view, i restarted Geogebra and that did fix the Laplace[sin(a*t)] problem. The problem still occurs with defining f(t):= exp(t/τ)sin(2πγt) and then taking its Laplace transform as Laplace[f,t]. The result returned was "--> ?". Just now i replaced (t/τ) with (A*t), so that the new function reads c(t):= exp(A*t)*sin(2*π*γ*t). I ran Laplace on the new function, c, as Laplace[c,t], and it produced the correct result as verified against sagemath: ((2 * γ) * π / (A^(2) - ((2 * A) * t) + t^(2) + ((4 * γ^(2)) * π^(2)))). So, i'm still left with the original problem that Laplace in Geogebra won't work on the function defined earlier as f(t) using the expression (t/τ) but it will work with (A*t). And this is using a fresh version of Geogebra.

For what it's worth the same test in SageMath is

A = var('A')

F = var('F')

t = var('t')

s = var('s')

f=exp(A*t)*sin(2*pi*F*t)

f.laplace(t,s)

2*pi*F/(4*pi^2*F^2 + A^2 - 2*A*s + s^2)

Thanks for the help. 1

Sorry, that's a limitation of our CAS engine (not a priority to improve right now).