//Some useful equations
int main(){
  //area portion of a circle
  A = pi*r^2 * (theta/(2*pi))
  //area chord of a circle
  A = R * R * acos((R - h)/R) - (R - h) * sqrt(2 * R * h - h * h)
    // h is the height of the chord h = R - hypot(x,y)
  // rotation matrix counnterclockwise
  [x' y'] = [[cost -sint] [sint cost]][x y]
  // rotation matrix clockwise
  [x' y'] = [[cost sint] [-sint cost]][x y]
}

//Some useful equations
int main(){
  //area portion of a circle
  A = pi*r^2 * (theta/(2*pi))
  //area chord of a circle
  A = R * R * acos((R - h)/R) - (R - h) * sqrt(2 * R * h - h * h)
    // h is the height of the chord
  

}

--- 
+++ 
@@ -4,7 +4,9 @@
   A = pi*r^2 * (theta/(2*pi))
   //area chord of a circle
   A = R * R * acos((R - h)/R) - (R - h) * sqrt(2 * R * h - h * h)
-    // h is the height of the chord
-  
-
+    // h is the height of the chord h = R - hypot(x,y)
+  // rotation matrix counnterclockwise
+  [x' y'] = [[cost -sint] [sint cost]][x y]
+  // rotation matrix clockwise
+  [x' y'] = [[cost sint] [-sint cost]][x y]
 }
Add rotation matrix , clockwise and counterclockwise.
