Part E Now check your work by using the GeoGebra geometry tool to repeat parts A through D. Open GeoGebra, and complete each step below. If you need help, follow these instructions for using GeoGebra. You will take a screenshot of your work when you are through, so be sure to clearly label your construction as you work.

Plot points A, B, and C, and draw a polygon, ΔABC, through the points.
Draw a line perpendicular to A⁢C¯ through point B.
Label the intersection of the line perpendicular to A⁢C¯ through B and A⁢C↔ point D.
Measure and display the slopes of A⁢C↔ and B⁢D↔.
Display the equations of A⁢C↔ and B⁢D↔ in the Algebra margin.
Measure and display the lengths of A⁢C¯ and B⁢D¯.
Calculate and display the area of ΔABC.
Take a screenshot showing the geometric construction and the Algebra margin, save it, and insert the image in the space below.

Part F
Compare the calculations displayed in GeoGebra with the calculations you completed in parts A through D. Look in the Algebra margin too. Do the results in GeoGebra match the results you obtained earlier? If not, where do the discrepancies occur? You might have to rearrange equations algebraically to determine whether two equations match.

Part G
You’ve seen two methods for finding the area of ΔABC—using coordinate algebra (by hand) and using geometry software. How are the two methods similar? How are they different? Why might coordinate algebra be important in making and using geometry software?