Chapter 1.2, Problem 66PE

The general form of an equation of a circle is ${\left(x-h\right)}^2+{\left(y-k\right)}^2=r^2.$ If we solve the equation for x we get equation of the form $x=h\pm \sqrt{r^2-{\left(y-k\right)}^2.}$ The equation $x=h+\sqrt{r^2-{\left(y-k\right)}^2}$ represents the graph of the corresponding right side semicircle, and the equation $x=h-\sqrt{r^2-{\left(y-k\right)}^2}$ represents the graph of the left-side semicircle likewise, if we solve for y, we have $x=k\pm \sqrt{r^2-{\left(y-h\right)}^2}$ . These equations represent the top and bottom semicircles. For Exercise 65-68, graph the equations.

$\begin{array}{l}\text{a}.\text{}y=\sqrt{9-x^2}\\ \text{b}.y=-\sqrt{9-x^2}\\ \text{c}.x=\sqrt{9-y^2}\\ \text{d}.x=-\sqrt{9-y^2}\end{array}$