Blanchet Theorem

In triangle ABC, Point E is an arbitrary point on altitude AD. Move point A, B, C or E and observe what happens.

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Make a conjecture about your observation. Prove your conjecture.

Copying a Segment

Move the cursor slider to the right by interval 1 to copy segment AB. Can you see why AB is congruent to CD? Justify your answer.

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The construction above is a simulation of the compass and straightedge construction on how to copy a line segment.

Point inside an equilateral triangle

ABC is an equilateral triangle. Point D is a point in the same plane and three segments are connected to it where each segment is perpendicular to a side of the triangle as shown.

This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com

1.) Move A or B to choose the size of the equilateral triangle.
2.) Move point D. What do you observe.
3.) Repeat 1 and 2 several times. Is your observation still the same?
4.) Make a conjecture about your observation and try to see if you can prove it.

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Circumference of a circle

Move the slider to the extreme right and observe what happens.


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This is a demonstration that the circumference of a circle with radius 1 is equal to 2*pi or approximately 6.28.

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More than 50 GeoGebra Tutorials at Math and Multimedia