Evaluate the radius of a circle using the fact that this circle is tangent to the y-axis.
E
Practice makes perfect
We are given that point B is the center of a circle that is tangent to the y-axis. We also know that B has coordinates of (3, 1), and we want to evaluate the area of this circle.
Since the tangent line is perpendicular to the radius of the circle at the tangency point, we can conclude that the tangency point will occur at (0, 1).
Next we can use the Distance Formula to find the radius r. To do this let's substitute ( 3, 1) and ( , 1).
The radius of the circle is 3 units. Finally, recall the formula for the area of a circle.
A=π r^2
Let's substitute 3 for r in above formula.
A=π ( 3)^2=9π
The area of the circle is 9π square units. This corresponds with answer E.
