public void TestAbsDer()
{
Entity func = "abs(x + 2)";
var derived = func.Differentiate("x");
Assert.Equal(MathS.Signum("x + 2").Simplify(), derived.Simplify());
}
public void TestSignum2()
{
var expr = MathS.Signum(x) + 1;
var func = expr.Compile(x);
Assert.Equal(0, func.Call(-3));
}
[Fact] public void Signum()
=> Test(@"\operatorname{sgn}\left(x\right)", MathS.Signum(x));