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Cogito

Grade 8 Math · Chapter 2 · Lesson 4

Practice Worksheet

Angle-Angle Similarity

Two angles are enough.

10 problems · about 19 minutes · 8.G.A.5

NameDate

Figure — use these to answer the problems

Two angles of a triangle. Whatever is left of 180° is the third.
030609012015018050° + 60° = 110°
First angle50
Second angle60
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

3 problems

  1. From “Dilations on the Coordinate Plane”

    (4, −3) dilated by 5. What is the new y?

    Answer

  2. From “Similar Figures”

    Similar figures. 4 matches 10. Another side is 6. Its match?

    Answer

  3. From “Dilations”

    A side of 9 dilated by 3. New length?

    Answer

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. Angles 25° and 95°. What is the third?

    Answer

  2. Angles 30° and 80°. What is the third?

    Answer

  3. Angles 90° and 45°. What is the third?

    Answer

Build It Up

The same ideas with more to keep track of.

2 problems

  1. Do similar triangles have equal side lengths? 1 for yes, 0 for no.

    Answer

  2. A triangle with angles 60, 60 and what?

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

2 problems

  1. The Third Angle

    A triangle has angles 45° and 65°. What is the third, in degrees?

    Answer

  2. The Criterion

    How many matching angles are needed for similarity?

    Answer