Answer: x² + y² = a² + b².
- A x² + y² = a² + b²
- B x² + y² = a² - b²
- C x² + y² = a² × b²
- D x² + y² = 2ab
Correct answer: A. x² + y² = a² + b²
Explanation: Director circle is locus of points from which the two tangents to ellipse are perpendicular. Its equation: x² + y² = a² + b².
The slope of a line is the ratio of vertical change (rise) to horizontal change (run) between any two points on it - equivalently, the tangent of the angle θ the line makes with the positive x-axis.