Triangles

 

 
  • A triangle has three sides and three angles.
 
  • The three angles always add to 180°.

Equilateral, Isosceles and Scalene
 

There are three special names given to triangles that tell how many sides (or angles) are equal.

There can be 3, 2 or no equal sides/angles:

Equilateral Triangle

Three equal sides
Three equal angles, always 60°

Isosceles Triangle

Two equal sides
Two equal angles

Scalene Triangle

No equal sides
No equal angles

 

What Type of Angle?
 

Triangles can also have names that tell you what type of angle is inside:

Acute Triangle

All angles are less than 90°

Right Triangle

Has a right angle (90°)

Obtuse Triangle

Has an angle more than 90°

 

Combining the Names

Sometimes a triangle will have two names, for example:
 

Right Isosceles Triangle

Has a right angle (90°), and also two equal angles

Can you guess what the equal angles are?

 

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