# Quadrilateral Investigation (I)

- Author:
- Tim Brzezinski

- Topic:
- Angles, Parallelogram, Quadrilaterals

In the applet below, quadrilateral

*ABCD*has been designed so that**angle**(In fact, you can adjust the measures of these angles using the slider in the top left corner.)*A*and angle*C always*remain congruent.**Directions:**1) Move any of the**BIG POINTS**around so that**angle**2) If this is the case, what special kind of quadrilateral do you have? 3) Use the tools of GeoGebra to prove your response to (2) is true. 4) Again, use the tools of GeoGebra to prove your response to (2) is true. This time, use a manner different from the one you used in (3) above.*B*and angle*D*become congruent.## New Resources

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