Embedded Files
Materials
Materials
Sum of Angles in a Triangle flipbook (one per group)
Paper and something to write with to draw a triangle (one per person or pair)
Straight edge to draw triangle (one per person)
Scissors to cut out the triangle (one per person)
Tape to connect the three vertices from the triangle together (one dispenser per group)
Activity 2: Tear Off the Corners
Activity 2: Tear Off the Corners
1. Draw a triangle as big as you can on a piece of paper.
Note: Skip to Step 3 if you have your Folding activity triangle.
2. Use scissors to cut out your triangle.
3. Tear or cut off each vertex from your triangle.
4. Put the vertices together at one point with the edges touching.
5. Tape the corners together.
Reflection
Reflection
We can see that by combining all three angles from our triangle together, they appear to form a straight angle. That is, we have fairly compelling evidence that the sum of interior angle measures of our triangle add to 180 degrees.
This demonstration is not a proof because it only illustrates that the three angles of one specific triangle appears to form a straight angle. We have not given any deductive arguments that this will work for every triangle or that our angles do, in fact, combine to form 180 degrees exactly.
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