________
/ 2
/x\ x*\/ 4 - x
2*asin|-| + -------------
\2/ 2 2.0*asin(x/2) + 0.5*x*(4.0 - x^2)^0.5
________
/x\ / 2
4*asin|-| + x*\/ 4 - x
\2/
-------------------------
2 ________
/x\ / 2
4*asin|-| + x*\/ 4 - x
\2/
-------------------------
2