Knowing the basic properties of the functions Beta and Gamma, it is easy to obtain :
first integral = (1/2)*Beta(3/4 ; 1/2)
second integral = (1/2)*Beta(1/4 ; 1/2)
and the product of the integrals = pi.
I'm reviewing Meirovitch's "Methods of Analytical Dynamics," and I don't understand the commutation of the derivative from r to dr:
$$
\mathbf{F} \cdot d\mathbf{r} = m \ddot{\mathbf{r}} \cdot d\mathbf{r} = m\mathbf{\dot{r}} \cdot d\mathbf{\dot{r}}
$$