Examples of built-in Mathematica functions: Sin[x] , Cos[x], Tan[x], Log[x], Sinh[x], Cosh[x], ArcSin[x], ArcCos[x], ArcTan[x], Abs[x], Sign[x], LegendreP[n, x], BesselJ[m,kr], SphericalHarmonicY[l, m, theta, phi]. Example of defining your own function: F[x_]:= E^x Sin[a x] .