Circle Around a Triangle
Click on the 5th tab with picture of triangle. Then select "Polygon". Mark 3 points and you will draw a triangle.
Find the circumcenter by constructing the perpendicular bisectors.
Mark the circumcenter by finding the intersection of the perpendicular bisectors.
Draw a circle around the triangle.
We say "The circle is circumscribed about the triangle".
You should end up with a circle that is around the triangle and passes through all three of the vertices of the triangle. Why do you think the circle passes through all three of the vertices of the triangle?