Back to Use informal arguments to establish facts about angles and similarity of triangles — Problem 4 · Task Set 25

Use Informal Arguments to Establish Facts About Angles and Similarity of Triangles

Work through each section in order. Show your work where indicated, and state which angle relationship you used to find each answer.

Grade 8·23 problems·~40 min·Common Core Math - Grade 8·container·8-g-a-5

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Fluency Practice

Find each missing angle measure. State the relationship you used.

In triangle $ABC$ , angle $A = 40\degree$ and angle $B = 75\degree$ . In triangle $DEF$ , angle $D = 40\degree$ and angle $E = 75\degree$ . Are the triangles similar by the AA criterion?

Yes — two pairs of angles are equal, which is enough for AA similarity.

No — you must also check that the third pair of angles is equal.

No — you must also check that a pair of sides is equal.

There is not enough information to decide.