Question 896510
<pre>
{{{drawing(200,200,-1.2,1.2,-1.2,1.2, circle(0,0,1),
locate(-1,-.45,A),locate(0.05,.15,O),
line(0,1,-0.8660254,-0.5),locate(-.14,.75,"60°"),
line(-0.8660254,-0.5,0.8660254,-0.5),
line(0.8660254,-0.5,0,1),
green(line(0,0,0,-.5),
line(-0.8660254,-0.5,0,0)),
locate(-.6,-.3,"30°"),locate(-.42,-.03,4),
locate(0,-.5,B)


)}}}
Draw OB perpendicular to the bottom side at B.

Radius OA bisects 60° angle at A, so angle OAB = 30° 

AB is half the side.  OA is a radius = 4.

{{{AB/OA=cos("30°")}}}

{{{AB/4 = sqrt(3)/2}}}

{{{AB=4sqrt(3)/2}}}

{{{AB=2sqrt(3)}}}   <-- half a side

{{{SIDE=4sqrt(3)}}}, approximately 6.92820323

Edwin</pre>