Anyone care to explain the concept of gaussian quatrature? I've tried some websites but they're a little over my head. An example would be appreciated, thanks!
Well I know its a system of Legendre polynomials used to approximate functions, but I'm not sure of how to actually do it, if anyone knows I'd appreciate an explination.
Gaussian integration involves Hermite polynomials, Legendre polynomials, Laugarre polynomials amongst others. In general, the integral of a function \int f(x) g dx where g is a weighting function, which can be e^{-x}, e^{-x^2/2} etc... can be written as \sum_{i} f(x_i) w_i. The x_i are the roots of the polynomials you wsh to use to fit and w are weighting functions at those roots.
Look at the Numerical Recipies website and they explain it very well.
I'm reviewing Meirovitch's "Methods of Analytical Dynamics," and I don't understand the commutation of the derivative from r to dr:
$$
\mathbf{F} \cdot d\mathbf{r} = m \ddot{\mathbf{r}} \cdot d\mathbf{r} = m\mathbf{\dot{r}} \cdot d\mathbf{\dot{r}}
$$