Sigma Percentile
JEE Main 2021 (18 March Shift 1)
LEVELJEE Main

Animated Solution for Mathematics - Circles: Choose the correct statement about two circles whose equations are given below: and

Select Answer:

Visualized Solution

Problem Statement

  • Circle
  • Circle
  • Goal: Find the number of meeting points between and .

General Equation of a Circle

  • General Form:
  • The center of the circle is at .

Center of

  • Compare with the general form:
  • Center

Radius Formula

  • Radius
  • For , the constant term .

Radius of

Center of

  • For
  • Center

Radius of

  • Here,

Distance Between Centers

  • To find how circles interact, we find the distance between centers and .
  • Distance Formula:

Calculating

Condition for Touching Circles

  • Sum of radii:
  • Distance between centers:
  • Observation:

Final Conclusion

  • Since , the circles touch each other externally.
  • Therefore, they have exactly one meeting point.

The Sigma Insight: Standard and General Equation of a Circle

Solution Diagram

Analyzing the Setup

To understand the interaction between the two circles, we must first identify their fundamental properties: their centers and radii. The general equation of a circle is given by:
For a circle in this form, the center is and the radius is calculated as .

Decoding the Blueprints

For the first circle, , given by , we identify , , and .
The center is . The radius is:
For the second circle, , given by , we identify , , and .
The center is . The radius is:

The Geometric Bridge

Now that we have the centers and , we calculate the distance between them. Since the -coordinates are identical, the distance is simply the difference in the -coordinates:

The Moment of Truth

We compare the distance between the centers to the sum of the radii. We have and , so:
Since the distance between the centers is exactly equal to the sum of the radii (), the circles are in a state of perfect external tangency.
They touch at exactly one point. The circles do not overlap, nor are they separated by any distance.

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