Chapter 13.5, Problem 5ST1

To determine

To find: an equation of the circle

Answer to Problem 5ST1

The equation of the circle is $x^2+y^2=9^2$

Explanation of Solution

Given information: The center at the origin and the radius is $9$

Calculation:

  $\begin{array}{l}center\left(x_1,y_1\right)\text{ and radius }r\\ \Rightarrow {\left(x-x_1\right)}^2+{\left(y-y_1\right)}^2=r^2\\ \Rightarrow {\left(x-0\right)}^2+{\left(y-0\right)}^2=9^2\\ \Rightarrow x^2+y^2=9^2\end{array}$