diff --git a/ex-4/note.py b/ex-4/note.py
new file mode 100644
index 0000000..fa955c5
--- /dev/null
+++ b/ex-4/note.py
@@ -0,0 +1,24 @@
+import matplotlib.pyplot as plt
+import numpy             as np
+
+p_max = 10
+
+def f(x):
+    return x * np.log(p_max/x)/np.arctan(np.sqrt(p_max**2/x**2 - 1))
+
+
+def main():
+    x = np.arange(0, 10, 0.001)
+    y = f(x)
+
+    plt.rcParams['font.size'] = 20
+    plt.figure()
+    plt.title('Expected distribution', loc='right')
+    plt.ylabel('$\\langle |P_v| \\rangle$')
+    plt.xlabel('$P_h$')
+    plt.plot(x, y, c='#92182b')
+    plt.show()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/notes/images/expected.pdf b/notes/images/expected.pdf
new file mode 100644
index 0000000..5f17253
Binary files /dev/null and b/notes/images/expected.pdf differ