Solving Problem with Circles in Backyard: Center (1,-1.5), Radius sqrt(29.25)

  • Thread starter Imperil
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No problem, happy to help! In summary, the conversation discusses the location of two trees and a cat in a backyard, with the line segments between the cat and the trees always being perpendicular. The equation of the locus of the cat is a circle with center (1, -1.5) and radius sqrt(29.25).
  • #1
Imperil
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In a backyard, there are two trees located at grid points A(-2, 3) and B(4, -6). The family cat is walking in the backyard. The line segments between the cat and the two trees are always perpendicular. Find the equation of the locus of the cat.

My Answer:

slope PA = (y - 3) / (x + 2)
slope PB = (y + 6) / (x - 4)
slope PA = -1 / slope PB (since the lines between PA and PB are perpendicular)

(y - 3) / (x + 2) = -1 / [(y + 6) / (x - 4)]
(y - 3) / (x + 2) = -1 * (x - 4) / (y + 6)
(y - 3) / (x + 2) = (-x+4) / (y + 6)

(y - 3) (y + 6) = (x + 2)(-x + 4)
y^2 + 3y - 18 = -x^2 + 2x + 8
x^2 + y^2 - 2x + 3y - 26 = 0

x^2 - 2x + 1 + y^2 + 3y + 2.25 = 26 + 1 + 2.25
(x - 1)^2 + (y + 1.5)^2 = 29.25

Therefore the cat is walking in a circle with center (1, -1.5) and radius sqrt(29.25).

I believe that my answer is incorrect but is there something I am missing? I have tried doing this question multiple times and I still can't find the correct answer.

EDIT: corrected a typo
 
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  • #2
Imperil said:
(y - 3) (y + 6) = (x + 2)(-x + 4)
y^2 + 3y - 18 = -x^2 + 2x + 8
x^2 + y^2 - 2x + 3y - 10 = 0

-18 - 8 = -26, not -10.
 
  • #3
Sorry yes that was a typo from a mistake I made on an old page.

I just checked by using x = 1 for a point on the circle and I believe that my answer is correct the way I have it (I edited the mistake)? I just tested with x=1 point on the circle and the lines now seem to be perpendicular
 
  • #4
Yes, your answer is correct.
 
  • #5
Thanks so much dx I really appreciate your time :)
 

Related to Solving Problem with Circles in Backyard: Center (1,-1.5), Radius sqrt(29.25)

1. What is the formula for finding the circumference of a circle?

The formula for finding the circumference of a circle is C = 2πr, where C is the circumference and r is the radius. In this case, the radius is sqrt(29.25), so the circumference would be approximately 18.17 units.

2. How do you find the area of a circle?

The formula for finding the area of a circle is A = πr^2, where A is the area and r is the radius. In this case, the area of the circle would be approximately 668.08 square units.

3. How do you determine if a point is inside or outside of a circle?

To determine if a point is inside or outside of a circle, you can use the distance formula: d = sqrt((x2-x1)^2 + (y2-y1)^2), where d is the distance between the two points (x1,y1) and (x2,y2). If the distance is less than the radius of the circle, then the point is inside the circle. If the distance is greater than the radius, then the point is outside the circle.

4. How do you find the coordinates of the center of a circle?

The coordinates of the center of a circle can be found by using the formula (h,k), where h is the x-coordinate and k is the y-coordinate. In this case, the center of the circle is located at (1,-1.5).

5. How can you use circles to solve real-world problems?

Circles can be used to solve real-world problems in a variety of ways. For example, you can use circles to determine the distance between two points, find the area of a circular pool, or calculate the amount of fencing needed for a circular garden. In this case, the problem could involve finding the area of a circular backyard and using that information to plan landscaping or construction projects.

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