Convert `x^2-y^2=4` into a polar equation.

Explanation

To convert the Cartesian equation \( x^2 - y^2 = 4 \) into a polar equation, we can follow these steps:

### Step 1: Substitute the polar coordinates
In polar coordinates, we have the following substitutions:
- \( x = r \cos \theta \)
- \( y = r \sin \theta \)

### Step 2: Substitute into the equation
...