Incircle of a triangle
Task
Construct the incircle of a triangle.
Explore the construction below and explore how to create the incircle of a triangle with Geometry in GeoGebra Calculator Suite. Then try it yourself by following the instructions below.
Explore the construction...
Instructions
Note: If you're using the Mobile App make sure that the chosen Labeling option is New Points Only. You can change this by going to the Settings in the app's menu and then selecting General.
| 1. |  | Create a triangle ABC using the Polygon tool. |
| 2. |  | Select the Angle Bisector tool and create the angle bisector for two angles of the triangle. Hint: Selecting the three points A, B, and C produces the angle bisector of the enclosed angle. |
| 3. |  | Create the intersection point D of the two angle bisectors using the Intersect tool. |
| 4. |  | Select the Perpendicular Line tool and create a perpendicular line to one side of the triangle, through point D. |
| 5. | | Create the intersection point E of the perpendicular line and the chosen side of the triangle using the Intersect tool. |
| 6. |  | Select the Circle with Center tool and construct the incircle with center D through point E. |
| 7. |  | Hide the auxiliary lines used for the construction. |
| 8. |  | Connect points D and E using the Segment tool to display the radius of the incircle. |
| 9. |  | Show the right angle between the incircle's radius and the corresponding side of the triangle using the Angle tool. |
| 10. |  | Select the Move tool and drag the vertices of the triangle to check if your construction is correct. |