A circle centered at [tex]$(-1, 2)$[/tex] has a diameter of 10 units. Amit wants to determine whether [tex]$(2, -2)$[/tex] is also on the circle. His work is shown below.

1. The radius is 5 units.
2. Find the distance from the center to [tex]$(2, -2)$[/tex]:
[tex]\[
\begin{array}{l}
\sqrt{(-1-2)^2 + (2-(-2))^2} \\
\sqrt{(-3)^2 + (4)^2} = \sqrt{9 + 16} = 5
\end{array}
\][/tex]

The point [tex]$(2, -2)$[/tex] lies on the circle because the calculated distance is the same as the radius.

Is Amit's work correct?
A. No, he should have used the origin as the center of the circle.
B. No, the radius is 10 units, not 5 units.
C. No, he did not calculate the distance correctly.
D. Yes, the distance from the center to [tex]$(2, -2)$[/tex] is the same as the radius.



Answer :

Amit's work and his approach contain a mistake in the calculation of the distance between the center of the circle [tex]\((-1, 2)\)[/tex] and the given point [tex]\((2, -2)\)[/tex].

Let’s walk through the correct steps:

1. Understand the Problem: We need to find out whether the point [tex]\((2, -2)\)[/tex] is on the circle centered at [tex]\((-1, 2)\)[/tex] with a radius of 5 units.

2. Determine the Radius: The diameter of the circle is given as 10 units. Therefore, the radius of the circle is:
[tex]\[ \text{radius} = \frac{\text{diameter}}{2} = \frac{10}{2} = 5 \text{ units} \][/tex]

3. Find the Distance From the Center to the Point: Use the distance formula to calculate the distance between the center [tex]\((-1, 2)\)[/tex] and the point [tex]\((2, -2)\)[/tex]:
[tex]\[ \text{Distance} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \][/tex]
Substituting [tex]\((x_1, y_1) = (-1, 2)\)[/tex] and [tex]\((x_2, y_2) = (2, -2)\)[/tex]:
[tex]\[ \text{Distance} = \sqrt{(2 - (-1))^2 + (-2 - 2)^2} \][/tex]
Simplifying inside the square root:
[tex]\[ \text{Distance} = \sqrt{(2 + 1)^2 + (-2 - 2)^2} = \sqrt{3^2 + (-4)^2} \][/tex]
Calculating further, we get:
[tex]\[ \text{Distance} = \sqrt{9 + 16} = \sqrt{25} = 5 \text{ units} \][/tex]

4. Compare Distance with Radius: The calculated distance from the center [tex]\((-1, 2)\)[/tex] to the point [tex]\((2, -2)\)[/tex] is 5 units.

Since the calculated distance (5 units) is equal to the radius of the circle (5 units), the point [tex]\((2, -2)\)[/tex] lies on the circle.

Therefore, Amit’s conclusion is incorrect. The correct conclusion should be:
[tex]\[ \text{Yes, the point } (2, -2) \text{ does lie on the circle because the distance from the center is equal to the radius.} \][/tex]

Amit did not calculate the distance correctly. The correct distance calculation shows that the point [tex]\((2, -2)\)[/tex] is indeed on the circle, as the distance is exactly 5 units, which matches the radius of the circle.