Math  /  Geometry

QuestionQuestion Find the center and radius of the circle represented by the equation below. (x13)2+(y+11)2=361(x-13)^{2}+(y+11)^{2}=361
Answer Attempt 1 out of 2
Center: \square \square )
Radius: \square

Studdy Solution

STEP 1

What is this asking? We're looking for the center and radius of a circle given its equation. Watch out! Don't mix up the signs of the coordinates of the center!

STEP 2

1. Recall the standard equation of a circle.
2. Identify the center.
3. Determine the radius.

STEP 3

The **standard equation** of a circle is given by (xh)2+(yk)2=r2,(x - h)^2 + (y - k)^2 = r^2, where (h,k)(h, k) is the **center** of the circle and rr is its **radius**.
This equation tells us how far each point (x,y)(x, y) on the circle is from the center (h,k)(h, k).
It's like a distance formula, but specifically for circles!

STEP 4

Let's **compare** our given equation, (x13)2+(y+11)2=361,(x - 13)^2 + (y + 11)^2 = 361, with the standard equation.
Notice that y+11y + 11 can be rewritten as y(11)y - (-11).
This helps us see that h=13h = \mathbf{13} and k=11k = \mathbf{-11}.
So, the center of our circle is (13,11)(13, -11).
Remember, the signs in the standard equation are subtractions, so a plus sign in our equation means the corresponding coordinate is negative!

STEP 5

Our equation tells us that r2=361r^2 = \mathbf{361}.
To find the **radius** rr, we take the **principal square root** of both sides: r2=361.\sqrt{r^2} = \sqrt{361}. This gives us r=19r = \mathbf{19}, since 1919=36119 \cdot 19 = 361.
The radius is a distance, so it must be positive!

STEP 6

Center: (13,11)(13, -11) Radius: 1919

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