Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter F - Foundations: A Prelude to Functions - Section F.4 Circles - F.4 Assess Your Understanding - Page 38: 8

Answer

Center: $(1, 2)$ Radius = $2$ units Equation: $(x-1)^2+(y-2)^2=4$

Work Step by Step

The standard form of the equation of a circle is: $(x-h)^2+(y-k)^2=r^2$ where the center of the circle is $(h,k)$ and the radius is $r$. Here, the center of the circle is $(1,2)$ so $h=1$ and $k=2$. The radius can be calculated as the distance between the given point on the circle and the center. The distance formula can be applied here: $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$, where the points are $(x_1,y_1)$ and $(x_2,y_2)$ Here the distance is: $r=d=\sqrt{(1-1)^2+(2-0)^2}=\sqrt{0+4}=2$ Therefore the standard form of the equation is: $(x-1)^2+(y-2)^2=2^2$ $(x-1)^2+(y-2)^2=4$
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