How do calculate something like...

$\displaystyle \mathbb{E}[W_{\tfrac{1}{2}} W_{\tfrac{3}{4}}]$ ..?

Where $\displaystyle \{W_t\}_{t \geq 0}$ is a standard Brownian motion.

$\displaystyle \frac{1}{\sqrt{2 \pi 1/2} \sqrt{2 \pi 3/4}} \int_{-\infty}^{\infty} e^{-x^2}e^{-\frac{2x^2}{3}} dx$ ..?