Question

Which theorem or postulate proves that △ABC and △DEF are similar? SSS Similarity Theorem AA Similarity Postulate SAS Similarity Theorem Two triangles with the same shape. In the first triangle, the vertices are labeled as A, B, and C. Base is B C and the top vertex is A. Side A B is labeled 3. Side B C is labeled 7. Side A C is labeled 6. In the second triangle, the vertices are labeled as D, E, and F. Base is E F and the top vertex is D. Side D E is labeled 18. Side E F is labeled 42. Side D F is labeled 36

Answer 1

The theorem that proves that the two triangles are similar is the SAS Similarity Theorem. The theorem states that if two sides of one triangle are proportional to two sides of another triangle, and the included angle between these sides is the same in both triangles, then the two triangles are similar.

In this case, the ratio of the corresponding sides of the two triangles are:

AB/DE = 3/18 = 1/6

BC/EF = 7/42 = 1/6

Since the ratio of corresponding sides is equal, and the included angle between them (angle B and angle E) is the same, the two triangles are similar by the SAS Similarity Theorem.