Intersection Of A Circle And A Line
Overview
A straight line can slice through a circle at two points, just touch it at one, or miss it entirely. Which of these happens is decided by a single number from the quadratic you get when you combine their equations: the discriminant. This is coordinate geometry meeting the algebra of quadratics in a satisfying way.
In this lesson you will work with the equation of a circle \((x-a)^2+(y-b)^2=r^2\), substitute a line into it, and use the discriminant of the resulting quadratic to decide whether the line is a chord (two points), a tangent (one point) or misses the circle (none). One calculation settles the geometry.
Objectives
- Know and use the equation of a circle with centre (a, b) and radius r.
- Solve problems involving the intersection of a circle and a straight line.
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Lesson Evaluation
Congratulations on completing the lesson on Intersection Of A Circle And A Line. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- The equation of a circle with centre (a, b) and radius r is: A. (x - a)^2 + (y - b)^2 = r B. (x - a)^2 + (y - b)^2 = r^2 C. x^2 + y^2 = r D. (x + a)^2 + (y + b)^2 = r^2 Answer: B
- When a line is substituted into a circle, what does a discriminant of zero mean? A. The line is a chord B. The line is a tangent C. The line misses the circle D. The circle has no centre Answer: B
- For y = x + 1 and x^2 + y^2 = 25, the quadratic in x is x^2 + x - 12 = 0. Its discriminant is: A. -49 B. 1 C. 47 D. 49 Answer: D
- If the discriminant of the combined quadratic is negative, the line: A. Cuts the circle at two points B. Touches the circle C. Misses the circle D. Passes through the centre Answer: C
- A line cuts a circle at two points. The line is called a: A. Tangent B. Radius C. Chord D. Diameter Answer: C
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