# Triangle Exterior Angles: Quick Exploration

- Author:
- Tim Brzezinski

## In the GeoGebra app below,

1) Use the POLYGON tool to construct triangle

*ABC*. 2) Select the RAY tool. Construct a ray with endpoint*A*that passes through*B*. Construct a ray with endpoint*B*that passes through*C*. Construct a ray with endpoint*C*that passes through*A*. 3) Select the POINT ON OBJECT tool. Plot a point*D*on ray*AB*that does not lie between*A*and*B*. Plot a point*E*on ray*BC*that does not lie between*B*and*C*. Plot a point*F*on ray C*A*that does not lie between*C*and*A*. Keep going! More directions appear below this app.4) Select the ANGLE tool. Then select points

*D*,*B*,*C*(in that order). This is one exterior angle of this triangle. 5) Find and display the measures of the other 2 exterior angles of this triangle. 6) Go to the ALGEBRA view. Now calculate the sum of the measures of these 3 exterior angles.Select the MOVE tool. Move any one (or more) of the triangle's vertices around.
What can we conclude about the sum of the measures of the **exterior angles** of this triangle? *Be specific in your response! *