When determining if two triangles are similar under dilation, we typically refer to the Angle-Angle criterion, denoted as AA~. According to the AA criterion, if two angles of one triangle are equal to two angles of another triangle, then the two triangles are similar.
Answer:
AA~ (Angle-Angle Similarity)
Explanation and Proof:
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Understanding Dilation: Dilation is a transformation that alters the size of a figure but maintains its shape. This means that the angles of the original triangle remain the same after dilation, while the sides are proportionally scaled.
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Identifying Angles: Let’s denote triangle ABC and triangle A'B'C' where triangle A'B'C' is a dilation of triangle ABC centered at a point O, with a scale factor k (where k > 0).
- Triangle ABC has angles ∠A, ∠B, and ∠C.
- Triangle A'B'C' has corresponding angles ∠A', ∠B', and ∠C'.
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Proving Angle Equality: Since dilation does not change the angles, it follows that:
- ∠A = ∠A'
- ∠B = ∠B'
- ∠C = ∠C'
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Applying AA Criterion: To prove that triangles ABC and A'B'C' are similar, we note:
- We have established that two angles of triangle ABC (∠A and ∠B) are equal to two angles of triangle A'B'C' (∠A' and ∠B').
- According to the AA similarity criterion, if two angles of one triangle are equal to two angles of another triangle, the triangles are similar.
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Conclusion: Therefore, by the AA~ criterion, triangles ABC and A'B'C' are similar.
In conclusion, the similarity criterion that proves two triangles are similar in the context of dilation is AA~ (Angle-Angle Similarity).