diff --git a/A/4/kinematics_check.py b/A/4/kinematics_check.py
index 3f61a25..f66baa0 100644
--- a/A/4/kinematics_check.py
+++ b/A/4/kinematics_check.py
@@ -9,11 +9,17 @@ from matplotlib.patches import Rectangle
 import multiprocessing
 
 
-class GoodOrbit(Orbit):
+class BetterOrbit(Orbit):
 
   def __init__(self):
     self.kAlpha = mp.mpf("1.7") / (2 * mp.pi)
-    self.kCriticalTheta = 2.86 / ((2 / 3) * self.kAlpha) - 0.1
+    def f(x):
+      r=(1/3)*self.kAlpha*mp.sqrt(1+x**2)
+      phi=mp.atan(x)
+      L=mp.mpf("2.86")
+      return (r+3*r*mp.cos(mp.pi-2*phi)-L)**2+(3*r*mp.sin(mp.pi-2*phi))**2-L**2
+    self.kCriticalTheta = mp.findroot(f, 15, solver='secant')
+    print(f"CriticalTheta={self.kCriticalTheta}", file=sys.stderr)
     self.r = (1 / 3) * self.kAlpha * mp.sqrt(1 + self.kCriticalTheta**2)
     self.point_A_cartesian = (
         self.kAlpha * self.kCriticalTheta * mp.cos(self.kCriticalTheta),
@@ -179,7 +185,7 @@ class GoodOrbit(Orbit):
 
 
 if __name__ == "__main__":
-  orbit = GoodOrbit()
+  orbit = BetterOrbit()
   loong = Loong(orbit, 224, mp.mpf("2.0"), mp.mpf("1e-8"))
   res_list = []
   for ti in np.arange(5, 10, 0.025):
diff --git a/A/4/simulator.py b/A/4/simulator.py
index 99670da..b2d409c 100644
--- a/A/4/simulator.py
+++ b/A/4/simulator.py
@@ -13,7 +13,13 @@ class GoodOrbit(Orbit):
 
   def __init__(self):
     self.kAlpha = mp.mpf("1.7") / (2 * mp.pi)
-    self.kCriticalTheta = 2.86 / ((2 / 3) * self.kAlpha)
+    def f(x):
+      r=(1/3)*self.kAlpha*mp.sqrt(1+x**2)
+      phi=mp.atan(x)
+      L=mp.mpf("2.86")
+      return (r+3*r*mp.cos(mp.pi-2*phi)-L)**2+(3*r*mp.sin(mp.pi-2*phi))**2-L**2
+    self.kCriticalTheta = mp.findroot(f, 15, solver='secant')
+    print(f"CriticalTheta={self.kCriticalTheta}", file=sys.stderr)
     self.r = (1 / 3) * self.kAlpha * mp.sqrt(1 + self.kCriticalTheta**2)
     self.point_A_cartesian = (
         self.kAlpha * self.kCriticalTheta * mp.cos(self.kCriticalTheta),