public void TestDeriveSineInv()
{
Expression <Func <double, double> > lambda = x => Math.Sin(1d / x);
PartialDerivative pd = new PartialDerivative();
Expression derivative = pd.Differentiate(lambda.Body, "x");
Assert.AreEqual(ExpressionType.Multiply, derivative.NodeType);
Assert.AreEqual("(-(1 / (x * x)) * Cosine((1 / x)))", derivative.ToString());
}
public void TestDeriveSine()
{
Expression <Func <double, double> > lambda = x => Math.Sin(x);
PartialDerivative pd = new PartialDerivative();
Expression derivative = pd.Differentiate(lambda.Body, "x");
Assert.AreEqual(ExpressionType.Call, derivative.NodeType);
Assert.AreEqual("Cosine(x)", derivative.ToString());
}
public void TestDeriveLinear()
{
Expression <Func <double, double> > lambda = x => 2 * x + 5;
PartialDerivative pd = new PartialDerivative();
Expression derivative = pd.Differentiate(lambda.Body, "x");
Assert.AreEqual(ExpressionType.Constant, derivative.NodeType);
Assert.AreEqual("2", derivative.ToString());
}
public void TestDeriveCosineProduct()
{
Expression <Func <double, double, double> > lambda = (x, y) => Math.Cos(x) * Math.Sin(y);
PartialDerivative pd = new PartialDerivative();
Expression derivative = pd.Differentiate(lambda.Body, "x");
Assert.AreEqual(ExpressionType.Multiply, derivative.NodeType);
Assert.AreEqual("(-Sine(x) * Sin(y))", derivative.ToString());
/*
* NOTE: The reason why the first is named "Sine" while the second uses "Sin" is
* that Math.NET Palladium always uses the Math.NET Iridium trigonometric functions
* (MathNet.Numerics.Trig.Sine(x)). However, the second instance (System.Math.Sin)
* was not touched by Palladium at all and therefore is still using Math.Sin.
*/
}