This is an incorrect proof that all isosceles triangles are similar. Explain why the proof is incorrect.
Step 1. Draw 2 isosceles triangles and where and .
Step 2. Dilate triangle to a new triangle using center and a scale factor of , so that .
Step 3. Translate by directed line segment to take to a new triangle . Because translation preserves distance, and .
Step 4. Because , we can rotate using center to take to .
Step 5. Because , we can rotate using center to take to .
Step 6. We have now established a sequence of dilations, translations, and rotations that takes to , to , and to , so the triangles are similar.
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Problem 2
Student Task Statement
Which statement provides a valid justification for why all circles are similar?
All circles have the same shape—a circle—so they must be similar.
All circles have no angles and no sides, so they must be similar.
I can translate any circle exactly onto another, so they must be similar.
I can translate the center of any circle to the center of another, and then dilate from that center by an appropriate scale factor, so they must be similar.