Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 1 - Section 1.8 - Inverse Functions - Exercise Set - Page 272: 104

Answer

See below:

Work Step by Step

The general equation of a circle when it has a center other than the origin is $\left( x-{{h}^{2}} \right)+{{\left( y-k \right)}^{2}}={{r}^{2}}.$ Here, $\left( h,k \right)$ is the center of the circle and r is the radius of the circle. Put $\left( h,k \right)=\left( -1,1 \right)$ and $r=1$ in the general equation of the circle: $\begin{align} & {{\left( x-1 \right)}^{2}}+{{\left( y-\left( -1 \right) \right)}^{2}}={{\left( 1 \right)}^{2}} \\ & {{\left( x-1 \right)}^{2}}+{{\left( y+1 \right)}^{2}}=1 \end{align}$ Now, simplify the above expression: $\begin{align} & {{\left( x-1 \right)}^{2}}+{{\left( y+1 \right)}^{2}}=1 \\ & {{x}^{2}}+1-2x+{{y}^{2}}+1+2y=1 \\ & {{x}^{2}}+{{y}^{2}}-2x+2y+2=1 \end{align}$ So, the center is $\left( 1,-2 \right)$ and radius is $1$. The equation ${{\left( x-1 \right)}^{2}}+{{\left( y+1 \right)}^{2}}=1$ can be written as follows: $y=\sqrt{1-{{\left( x-1 \right)}^{2}}}-1.$ Put $x=0$ in the above equation: $\begin{align} & y=\sqrt{1-{{\left( 0-1 \right)}^{2}}}-1 \\ & =\sqrt{0}-1 \\ & =-1 \end{align}$ Place $x=1$ , $\begin{align} & y=\sqrt{1-{{\left( 1-1 \right)}^{2}}}-1 \\ & =\sqrt{1-0}-1 \\ & =\pm 1-1 \\ & =0,-2 \end{align}$ Place $x=2$ , $\begin{align} & y=\sqrt{1-{{\left( 2-1 \right)}^{2}}}-1 \\ & =\sqrt{1-{{\left( 1 \right)}^{2}}}-1 \\ & =\sqrt{0}-1 \\ & =-1 \end{align}$ Thus, the points $\left( 0,-1 \right),\left( 1,0 \right),\left( 1,-2 \right),$ and $\left( 2,-1 \right)$ satisfy the equation: $y=\sqrt{9-{{\left( x-1 \right)}^{2}}}-2.$
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