Radius question

Question

A circle has center (-2,3) and contains the point (1,8) what is the length of the radius ? 

Answer 1

A line segment from the center of a circle to a point on the circle is called a radius of the circle.

 

Use the distance formula (distance between two points):

    d = √((x₂ -x₁)² + (y₂ - y₁)²)   [note: this is based on the Pythagorean Theorem]

 

radius = √((1-(-2))² + (8-3)²)

radius = √(9 + 25)

radius = √34

 

This is approximately 5.83

Answer 2

The length of the radius is just the distance from the center to a point on the circle.

So use the distance formal to solve.

r²=(x₂-x₁)²+(y₂-y₁)²