Circle Passes through the Origin and Centre Lies on x-axis

We will learn how to find the equation of a circle passes through the origin and centre lies on x-axis.

The equation of a circle with centre at (h, k) and radius equal to a, is (x - h)$^{2}$ + (y - k)$^{2}$ = a$^{2}$.

When the circle passes through the origin and centre lies on x-axis i.e., h = a and k = 0.

Then the equation (x - h)$^{2}$ + (y - k)$^{2}$ = a$^{2}$ becomes (x - a)$^{2}$ + y$^{2}$ = a$^{2}$

Circle Passes through the Origin and Centre Lies on x-axis

If a circle passes through the origin and centre lies on x-axis then the abscissa will be equal to the radius of the circle and the y co-ordinate of the centre will be zero. Hence, the equation of the circle will be of the form:

(x - a)$^{2}$ + y$^{2}$ = a$^{2}$

⇒ x$^{2}$ + y$^{2}$ - 2ax = 0

Solved example on the central form of the equation of a circle passes through the origin and centre lies on x-axis:

1. Find the equation of a circle passes through the origin and centre lies on y-axis at (0, -2).

Solution:

Centre of the lies on y-axis at (0, -2)

Since, circle passes through the origin and centre lies on x-axis then the abscissa will be equal to the radius of the circle and the y co-ordinate of the centre will be zero.

The required equation of the circle passes through the origin and centre lies on y-axis at (0, 2) is

(x + 7)$^{2}$ + y$^{2}$ = (-7)$^{2}$

⇒ x$^{2}$ + 14x + 49 + y$^{2}$ = 49

⇒ x$^{2}$ + y$^{2}$ + 14x = 0

2. Find the equation of a circle passes through the origin and centre lies on x-axis at (12, 0).

Solution:

Centre of the lies on x-axis at (12, 0)

Since, circle passes through the origin and centre lies on x-axis then the abscissa will be equal to the radius of the circle and the y co-ordinate of the centre will be zero.

The required equation of the circle passes through the origin and centre lies on x-axis at (12, 0) is

(x - 12)$^{2}$ + y$^{2}$ = 12$^{2}$

⇒ x$^{2}$ - 24x + 144 + y$^{2}$ = 144

⇒ x$^{2}$ + y$^{2}$ - 24x = 0

● The Circle

• Definition of Circle
• Equation of a Circle
• General Form of the Equation of a Circle
• General Equation of Second Degree Represents a Circle
• Centre of the Circle Coincides with the Origin
• Circle Passes through the Origin
• Circle Touches x-axis
• Circle Touches y-axis
• Circle Touches both x-axis and y-axis
• Centre of the Circle on x-axis
• Centre of the Circle on y-axis
• Circle Passes through the Origin and Centre Lies on x-axis
• Circle Passes through the Origin and Centre Lies on y-axis
• Equation of a Circle when Line Segment Joining Two Given Points is a Diameter
• Equations of Concentric Circles
  
• Circle Passing Through Three Given Points
• Circle Through the Intersection of Two Circles
• Equation of the Common Chord of Two Circles
• Position of a Point with Respect to a Circle
• Intercepts on the Axes made by a Circle
• Circle Formulae
• Problems on Circle

11 and 12 Grade Math 

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