simplify("(x^2)^0.5") should be "abs(x)"

[paulftw]

While there are genuine use cases when returning "x" would be better (that's what most humans would expect), strictly speaking it is incorrect.

To reproduce in the mathnotepad:

derivative("(x^2)^0.5", "x").evaluate({x:-3})
    1

derivative("(x^2)^0.5", "x", {simplify:false}).evaluate({x:-3})
    -1

Here I evaluate the same derivative at the same point x=-3 but get two different results.
Same problem for x^4 and I assume all other even powers.

[josdejong]

Thanks that is a very good and valid point.

Anyone able to improve simplify? Help would be welcome.