# Circle Equations

## Recognise and use the equation of a circle with centre at the origin and the equation of a tangent to a circle.

##### Level 1Level 2Exam-StyleDescriptionHelpMore Graphs

This is level 1: equations of circles.

 1) Which of the following is the equation of the circle above?a) $$x^2 + y^2 = 16$$b) $$x^2 + y^2 = 4$$c) $$x^2 + y^2 = 8$$ 2) The equation of a circle is $$x^2 + y^2 = 64$$. What is the radius of the circle? 3) The equation of a circle is $$x^2 + y^2 = 12.25$$. What is the radius of the circle? 4) Which of the following is the equation of a circle with centre at the origin and a radius of 11 units?a) $$x^2 + y^2 = 121$$b) $$x^2 + y^2 = 11$$c) $$x^2 + y^2 = 22$$ 5) The equation of a circle is $$5x^2 + 5y^2 = 125$$. What is the radius of the circle? 6) The equation of a circle is $$9x^2 + 9y^2 = 729$$. What is the radius of the circle? 7) Which of the following is the equation of a circle with centre at the origin and a radius of 6 units?a) $$2x^2 + 2y^2 = 36$$b) $$x^2 + y^2 = 6$$c) $$2x^2 + 2y^2 = 72$$ 8) Which of the following is the equation of a circle with centre at the origin which passes through the point (3,4)?a) $$16x^2 + 16y^2 = 25$$b) $$8x^2 + 8y^2 = 200$$c) $$24x^2 + 24y^2 = 25$$ 9) Which of the following is the equation of a circle with centre at the origin and a radius of $$2 \sqrt{2}$$ units?a) $$2x^2 + 2y^2 = 4$$b) $$2x^2 + 2y^2 = 8$$c) $$x^2 + y^2 = 8$$ 10) The equation of a circle is given as $$y^2 = (5+x)(5-x)$$. What is the radius of the circle?
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This is Circle Equations level 1. You can also try:
Level 2

## Instructions

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## Description of Levels

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Level 1 - Equations of circles

Level 2 - Equations of tangents to circles

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## Example

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