/// <summary>
/// Differentiates the specified expression.
/// </summary>
/// <param name="expression">The expression.</param>
/// <param name="variable">The variable.</param>
/// <returns>Returns the derivative.</returns>
protected virtual IExpression Abs(Abs expression, Variable variable)
{
var div = new Div(expression.Argument.Clone(), expression.Clone());
var mul = new Mul(_Differentiate(expression.Argument.Clone(), variable), div);
return mul;
}
