Understanding Check
Use the GeoGebra application below to construct
the circumscribing circle about the rectangle.
 Click on the down arrow of the construction
to open
the construction menu. Select the Angle Bisector
menu item. Then click on points B, A, then C. You
have constructed the angle bisector of angle BAC.
 Now click on point A, B, then C. You have constructed the angle bisector of angle ABC.
 Click on the down arrow of the Point menu button
.
Select the Intersect Two Objects
menu button. Click on each of the two angle bisectors. Point D that appears
at the intersection of the two angle bisectors is the
incenter.
 Click on the arrow in the angle bisector menu button
to open the construction menu. Click on the perpendicular line menu button
.
Now click on the incenter (point C) then one side of the triangle. The point where the
perpendicular line intersects the side of the triangle is on the incircle.
 Click on the Intersect Two Objects
button, then click on the perpendicular line, and the side to which it is perpendicular.
Point E appears. Point E is on the incircle.
 Click on the Circle With Center Through Point
.
Then click on the incenter (point D) then point E. The circle that is drawn is the
incircle.
To change the manipulative, first click on the arrow
menu button.
Then click on the blue points and drag them to change the figure.
