Find the locus of a point which moves such that its distance from the origin is three times is the distance from the x-axis.
Key points to solve the problem:
• Idea of distance formula- Distance between two points A(x1,y1) and B(x2,y2) is given by- AB =
How to approach: To find the locus of a point we first assume the coordinate of the point to be (h, k) and write a mathematical equation as per the conditions mentioned in the question and finally replace (h, k) with (x, y) to get the locus of the point.
Let the coordinates of a point whose locus is to be determined to be (h, k)
As we need to maintain a distance of (h,k) from origin such that it is 3 times the distance from the x-axis.
So we select a point (h,0) on the x-axis.
From distance formula:
Distance of (h,k) from (0,0) =
Distance of (h,k) from (h,0) =
According to question both distances are same.
∴
Squaring both sides:
h2 + k2 = 9k2
⇒ h2 = 8k2
Replace (h,k) with (x,y)
Thus, the locus of a point is x2 = 8y2 …….ans