109 correct calculation in units and quantities

episodes/05-units_and_quantities.md

@@ -104,7 +104,7 @@ This enables the use of arithmetic operations when quantities have compatible un
 
 ```python
 distance_start = 10 * u.mm
-distance_end = 23 * u.km
+distance_end = 20 * u.km
 length = distance_end - distance_start
 print(length)
 ```
@@ -349,6 +349,8 @@ angle in degrees: 90.0; and in radians: 1.5707963267948966
 Now we can pass the angle directly to `np.sin` without having to convert directly to radians:
 
 ```python
+import numpy as np
+
 print(f'sin of 90 degrees is: {np.sin(angle)}')
 print(f'sin of pi/2 radians is: {np.sin(1.57079632)}')
 print(f'sin of 90 degrees is not: {np.sin(90)}')
@@ -376,7 +378,10 @@ angles = np.arange(181) * u.deg
 ```
 
 ```python
+import matplotlib.pyplot as plt
+
 plt.plot(angles, np.sin(angles))
+plt.show()
 ```
 
 ![](fig/sin_curve_deg.png){alt='Plot of sin curve for degrees between 0-180'}