Question
The differential equation of all circles which pass through the origin and whose centre lies on y-axis is
Hint:
We have to find the differential equation of circle who has center at y-axis and is touching the origin. We will first write the equation of the circle. Then we will differentiate and find the value.
The correct answer is:
Let the center be at point (0,a).
So, the equation of the circle with its center on y axis will be
(x - 0)2 + (y - a)2 = a2
As the center is at distance a from origin and the circle is touching the origin, it's radius will be a.
The equation is
x2 + (y - a)2 = a2
We will expand the equation.
x2 + y2 - 2ay + a2 = a2
x2 + y2 - 2ay = 0 ...(1)
We will differentiate the above equation.
2x + 2y - 2a = 0.
2x + 2y = 2a. ...(2)
We will find the value of 2a from equation (1)
We will substitute this value in equation (2)
This is the required differential equation of family of circles with center at y-axis and touching the origin.
For such questions, we should know the equation of cricle with its centre at a point other than origin.
Related Questions to study
The differential equation of all parabolas whose axis are parallel to y-axis is
For such questions, we should know how to write the equation of a parabola. The axis of parabola can be parallel to x or y axis. So, we have to write the equation accordingly.
The differential equation of all parabolas whose axis are parallel to y-axis is
For such questions, we should know how to write the equation of a parabola. The axis of parabola can be parallel to x or y axis. So, we have to write the equation accordingly.
Solution of the differential equation is given by
When we get multipliction of two brackets equal to zero, any of the bracket can be zero or both of the brackets can be zero. It is decided based on the conditions in the equation.
Solution of the differential equation is given by
When we get multipliction of two brackets equal to zero, any of the bracket can be zero or both of the brackets can be zero. It is decided based on the conditions in the equation.