Answer
This is true.
Work Step by Step
let x = $\sqrt a$ and $y = \sqrt b$, so $x^2 = a, y^2 = b$. We seek to show $xy$ is equal to $\sqrt {ab}$. We know that $x^2*y^2 = ab$, so $(xy)^2 = ab$, so $xy = \sqrt {ab}$, and so $\sqrt a \sqrt b = \sqrt{ab}$, as was to be shown.
