1 : What postulate or theorem can be used to prove △PQR ~ △STU ??
Angle-Angle (AA) Similarity Postulate
Side-Side-Side (SSS) Similarity Theorem
Side-Angle-Side (SAS) Similarity Theorem
2 : Are the triangles similar?
No. The triangles are not similar.
Yes, by using Angle-Angle (AA) Similarity Postulate
Yes, by using Side-Angle-Side (SAS) Similarity Theorem
Yes, by using Side-Side-Side (SSS) Similarity Theorem
Firat slide is for #1, and second one is for #2

