Question

Right triangle ABC is located in A(-1,-2), B(-1,1) and C(3,1) on a coordinate plane. what is the equation of a circle with radius AC?
A) (x+1)*2+(y+2)*2=9
B) (x+1)*2+(y+2)*2=25
C) (x-3)*2+(y-1)*2= 16
D) (x-3)*2+(y-1)*2=25

Answer 1

Answer:  The equation of the circle is (x+1)²+(y+1)² = 25

Step-by-step explanation:  Use the Pythagorean Theorem to calculate the length of the radius from the coordinates given for the triangle location:  A(-1,-2), B(-1,1) and C(3,1)  The sides of the triangle are AB=3, BC=4, AC=5.

Use the equation for a circle: ( x - h )² + ( y - k )² = r², where ( h, k ) is the center and r is the radius.

As the directions specify, the radius is AC, so it makes sense to use the coordinates of A (-1,-2) as the center.  h is -1, k is -2  The radius 5, squared becomes 25.

Substituting those values, we have (x -[-1])² + (y -[-2])² = 25 .

When substituted for h, the -(-1) becomes +1 and the -(-2) for k becomes +2.

We end up with the equation for the circle as specified:

(x+1)²+(y+1)² = 25

A graph of the circle is attached. I still need to learn how to define line segments; the radius is only the segment of the line between the center (-1,-2) and (1,3)

Answer 2

Answer:

Hey there!

First, we want to find the radius of the circle, which equals the length of line segment AC.

Length of line segment AC, which we can find with the distance formula: $\sqrt{25$, which is equal to 5.

The equation for a circle, is: $(x-h)^2+(y-k)^2=r^2$, where (h, k) is the center of the circle, and r is the radius.

Although I don't know the center of the circle, I can tell you that it is either choice B or D, because the radius, 5, squared, is 25.

Hope this helps :) (And let me know if you edit the question)