2 / x \ _________
r *asin|---| / 2 2
\|r|/ x*\/ r - x
------------ + --------------
2 2 0.5*x*(r^2 - x^2)^0.5 + 0.5*r^2*asin(x/|r|)
_________
/ 2 2 2 / x \
x*\/ r - x + r *asin|---|
\|r|/
-----------------------------
2 _________
/ 2 2 2 / x \
x*\/ r - x + r *asin|---|
\|r|/
-----------------------------
2