invariant sum of squares

In the following applet:[br]How are points A, B, C and D defined?[br][br]How does changing the value of [math]m[/math] affect the sum [math]AC^2+BD^2[/math] ?[br]Now prove it!
ג1 עמוד 64 תרגיל 29

Információ: invariant sum of squares