# Define
var('y'); var('x')
f(x,y)= -(x*y)*exp(-(x^2 + y^2))
fdx(x,y) = derivative(f(x,y), x)
fdy(x,y) = derivative(f(x,y), y)
# Check
print f(x,y)-f(y,x)
# Compare these
print derivative(f(x,y), x).simplify_full()
print derivative(f(x,y), y).simplify_full()
This will print
0
(2*x^2 - 1)*y*e^(-x^2 - y^2)
(2*x*y^2 - x)*e^(-x^2 - y^2)
Why is this? I can add ".collect('x')" at end of second expression, but I
don't understand why it is not needed in first expression.
This is version 5.4.
--
Jori Mäntysalo
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