We'll make a pair of supplementary angles, have the computer measure each, and show how they always add up to 180°
Start by looking at the tools, arrow is for moving things, the dot makes points, the circle makes..., the segment tool makes segments, rays and lines, the letter tool labels things and writes text, and finally, the last tool is where you can make your own tools
Click on the segment tool and make a short horizontal segment.
Click on the text tool and then click on each point - see how they are labeled A and B?
Now make another segment, with the first point on the first segment (see how it lights up when you come near it?)
Label these points C and D
Move point D around...
double click on point C (the intersection) and change it to "X"
double click on point D (the free end of the segment) and change it to "C"
Now let's measure angles.
click the arrow tool, click on nothing, and then click (in the right order) the points that make up angle AXC. Use the menu bar to MEASURE the ANGLE.
Try changing the angle a bit...
Do the same now for angle BXC.
Do they always add up to 180°?
Let's find out - go to MEASURE / CALCULATE... (or use the keyboard shortcut). Click on the text that measures AXC, click "+", and click on the measurement of BXC. Click OK.
---- PROJECT -----
Construct two intersecting lines and show how all adjacent angles are supplementary, and how both pairs of vertical angles are congruent.
