<PRE><B>Question 996872</B>
I assume your rectangle is labeled in this manner
top left is B, top right is A, bottom right is N and bottom left is K
all 4 interior angles of a rectangle are 90 degrees each, I think your angle is really angle ASN since ANS is 90 degrees.
*******************************************************************************
triangle BAS and triangle KSN are equilateral triangles
triangle BSK and triangle ANS are isosceles triangles
******************************************************************************
side AS is 8 units and the altitude of triangle ANS drawn to side AN bisects angle ASN and side AN, therefore
sin(60) = (AN/2) / 8
16*sin(60) = AN
note that sin(60) = (1/2) * sqrt(3)
AN = 8 * sqrt(3)
 
 </PRE>