$\"\"$

The vertices of the ellipse is $\"\"$ and $\"\"$ .

In polar form, the equation of an ellipse with a focus at origin is $\"\"$ .

Substitute $\"\"$ in the above polar equation.

$\"\"$

Substitute $\"\"$ in the above polar equation.

$\"\"$

Divide equation (2) by equation (1).

$\"\"$

Substitute $\"\"$ in equation (1).

$\"\"$ \ \

Substitute $\"\"$ and $\"\"$ in $\"\"$ .

$\"\"$

The polar equation of the ellipse is $\"\"$ .