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

When the ellipse crosses $\"\"$ -axis, then $\"\"$ .

$\"\"$

The points are $\"\"$ .

Slope of the tangent is derivative of the ellipse.

$\"\"$ .

Differentiate on each side with respect to $\"\"$ .

$\"\"$

$\"\"$ .

Slope of the tangent line is at $\"\"$ : $\"\"$ .

Slope of the tangent line at $\"\"$ : $\"\"$ .

Since the two slopes are equal, then the tangent at these points are parallel.

The two slopes are equal, then the tangent at these points are parallel.