Question 706295
The other poster solved it for you, but I figured I'd draw out a pic for you so you can see what's going on.


Start with an equilateral triangle (note an equilateral triangle has three 60 degree angles, ie all angles are equal, and all sides are equal)


So let x = side length of equilateral triangle


We would get this pic if we drew out an equilateral triangle


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/Algebra%20dot%20com/1-25-20134-30-04PM_zpsea1bce0d.png">


Now cut the triangle in half. Pick any vertex and draw a perpendicular line to the opposite side. I'm going to pick the top vertex to get this


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/Algebra%20dot%20com/1-25-20134-30-20PM_zpsa3f0d887.png">


Note: the opposite side is cut in half, so the bottom side of x gets cut in half to get two equal pieces of {{{x/2}}}


Another Note: the top angle gets cut in half to get two equal 30 degree angles


So we have a 30-60-90 triangle with legs: {{{4}}} and {{{x/2}}}, the hypotenuse is {{{x}}} units