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Triangles Lesson

Triangle Quiz

Triangle Sort Game

Vocabulary mouseover for definition

Triangle

3 sided polygon totaling 180° Obtuse

Greater than 90° and less than 180° Acute

Less than 90° Right

Exactly 90° Degrees

the unit of measurement used to measure angles 180°

The sum of all angles of any triangle Congruent

same size, same shape, equal in length or measure Equilateral Triangle

All sides congruent Isoceles Triangle

2 sides congruent Scalene

No sides congruent or equal in length

Similar Content

Triangles Lesson

Triangle Quiz

Triangle Sort Game

Vocabulary mouseover for definition

Triangle

3 sided polygon totaling 180° Obtuse

Greater than 90° and less than 180° Acute

Less than 90° Right

Exactly 90° Degrees

the unit of measurement used to measure angles 180°

The sum of all angles of any triangle Congruent

same size, same shape, equal in length or measure Equilateral Triangle

All sides congruent Isoceles Triangle

2 sides congruent Scalene

No sides congruent or equal in length

A

An acute angle – less than 90°

An obtuse angle – greater than 90° and less than 180°

A right angle – exactly 90°

The box is the symbol for a right angle. This lets you know it is exactly 90 degrees and you don't have to use a protractor to check it.

Triangles can be classified by Side Length and/ or by Angle Measurement.

A triangle with all acute angles (all less than 90°) is an acute triangle.

A triangle with one obtuse angle (more than 90°) is an obtuse triangle.

A triangle with one right angle (90°) is a right triangle.

A triangle with 3 equal sides is an equilateral triangle.

A triangle with 2 equal sides is an isosceles triangle.

A triangle with no equal sides is a scalene triangle.

If a triangle has 2 congruent sides, then it also has 2 congruent angles.

Notice the picture below.