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Types of triangles review

Review ways to classify triangles based on their sides lengths and angles.  Practice classifying triangles.

Classifying triangles by their angles

Acute triangles

An acute triangle has 3 angles that each measure less than 90. Below are examples of acute triangles.
A triangle with angle measures of 44 degrees, 68 degrees, and 68 degrees. The degree labels for all 3 angles are highlighted.
A triangle with angle measures of 60 degrees, 60 degrees, and 60 degrees. The degree labels for all 3 angles are highlighted.

Right triangles

A right triangle has 1 angle that measures 90 and 2 acute angles. Below are examples of right triangles.
A triangle with angle measures of 90 degrees, 45 degrees, and 45 degrees. The 90 degrees angle label is highlighted.
A triangle with angle measures of 90 degrees, 54 degrees, and 36 degrees. The 90 degrees angle label is highlighted.

Obtuse triangles

An obtuse triangle has one angle that measures more than 90 and 2 acute angles. Below are examples of obtuse triangles.
A triangle with angle measures of 118 degrees, 31 degrees, and 31 degrees. The 118 degrees angle label is highlighted.
A triangle with angle measures of 104 degrees, 42 degrees, and 34 degrees. The 104 degrees angle label is highlighted.
Want to learn more about classifying triangles? Check out this video.
Problem 1A
Classify PQR by its angles.
A triangle PQR with angle measures of 112 degrees, 36 degrees, and 32 degrees.
Choose 1 answer:

Want to try more problems like this? Check out this exercise

Classifying triangles by their side lengths

Equilateral triangles

An equilateral triangle has three equal sides. Below are examples of equilateral triangles.
A triangle with side lengths of 10, 10, and 10 units.
A triangle with side lengths of 2, 2, and 2 units.

Isosceles triangles

An isosceles triangle has at least two equal sides. Below are examples of isosceles triangles.
A triangle with side lengths of 5, 5, and 4 units.
A triangle with side lengths of 5, 7, and 5 units.

Scalene triangles

A scalene triangle has no equal sides. Below are examples of scalene triangles.
A triangle with side lengths of 6, 9, and 7 units.
A triangle with side lengths of 4, 7, and 5 units.
Problem 2A
Classify PQR by its sides.
A triangle PQR. The angle at R has a box at its vertex connecting lines RP and RQ. Side RP is 5 units long, side RQ is 12 units long, and side PQ is 13 units long.
Choose all answers that apply:

Want to try more problems like this? Check out this exercise.

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