Find the following integrals and confirm by calculator:
4) $\int_{0}^{\sqrt{5}} \frac{x}{\sqrt{x^2+4}} dx$
5) $\int_{0}^{\pi/2} \sin x \sqrt{\cos x} dx$
6) $\int_{0}^{\pi/6} (1 + \sin x \cos x) dx$
7) $\int_{0}^{\sqrt{\pi/2}} x \sin(\pi - x^2) dx$
If $\int_{0}^{1} f(x) dx = 6$, $\int_{0}^{2} f(x) dx = 4$ and $\int_{2}^{4} f(x) dx = -8$, find
8) $\int_{0}^{2} f(2x) dx$
9) $\int_{0}^{2} f(\frac{1}{2}x) dx$
10) $\int_{1}^{2} f(2x) dx$
