check the picture below.
a circle has a total of 360°, if we split the circle with a hexagon's radii, each radii with their vertices will make an equilateral triangle who will have three 60° angles. Anyhow, if we run a line like the apothem "a" there, we'll end up with a 30-60-90 triangle, and then we can apply the 30-60-90 rule, as you see there.
since we know then that the distance from a vertex at the base to the center is 2, and the slant-height, sticking out from that vertex, is 6, then we can use the pythagorean theorem as you see in the picture, to get the distance V.