Classifying Triangles

You can classify a triangle by its angles and sides.

Equiangular all angles congruent

Acute all angles acute

Right one right angle

Obtuse one obtuse angle

Equilateral all sides congruent

Isosceles at least two sides congruent

Scalene no sides congruent

Example

What type of triangle is shown below?

At least two sides are congruent, so the triangle is isosceles. One angle is obtuse, so the triangle is obtuse. The triangle is an obtuse isosceles triangle.

Exercises

Classify each triangle by its sides and angles.

If possible, draw a triangle to fit each description. Mark the triangle to show known information. If you cannot draw the triangle, write not possible and explain why.

4. acute equilateral
5. right equilateral
6. obtuse scalene
7. acute isosceles
8. right isosceles
9. acute scalene

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