The center of a circle is at (0,0) and its radius is 5. Does the point (5,-2) lie on the circle?

1 Answer
Jan 18, 2016

No

Explanation:

A circle with center c and radius r is the locus (collection) of points which are distance r from c. Thus, given r and c, we can tell if a point is on the circle by seeing if it is distance r from c.

The distance between two points (x_1, y_1) and (x_2, y_2) can be calculated as
"distance" = sqrt((x_2-x_1)^2 + (y_2-y_1)^2)
(This formula can be derived using the Pythagorean theorem)

So, the distance between (0, 0) and (5, -2) is
sqrt((5-0)^2+(-2-0)^2) = sqrt(25+4) = sqrt(29)

As sqrt(29) != 5 this means that (5, -2) does not lie on the given circle.