Transforming the Purple Edge
The first step to build the T-Square animation is to move the purple edge continuously from its first position to its second.
Use this link to try animating the motion of just the purple edge to begin. The base square and rectangle are already there, so you can focus on just the animation components.
For example:
π΄ = π΄0 + π(π΄1 β π΄0)
π΅ = π΅0 + π(π΅1 β π΅0)
π΄ + π‘(π΅ β π΄) {0 β€ t β€ 1}
This task is exactly like the animation in the Parametric Thinking activity. You might or might not want to draw the dotted lines, and you can choose whether or not label the moving points. The labels have been provided in the Desmos sheet linked above, but you can turn them off.
You can now start to see that moving the square is simply a matter of moving the four lines.