Solve the programming task below in a Python markdown code block.
Below is a right-angled triangle:

```
  |\
  | \
  |  \
  |   \ 
o |    \ h 
  |     \
  |    θ \
  |_______\ 
     a
```

Your challange is to write a function (```missingAngle``` in C/C#, ```missing_angle``` in Ruby), that calculates the angle θ in degrees to the nearest integer. You will be given three arguments representing each side: o, h and a. One of the arguments equals zero. Use the length of the two other sides to calculate θ. You will not be expected to handle any erronous data in your solution.
Also feel free to reuse/extend the following starter code:
```python
def missing_angle(h, a, o):
```