Friday 8 February 2019

Triangles

Triangle with angles
right arrow 
A triangle has three sides and three angles 
right arrow 
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 32 or no equal sides/angles:
Equilateral Triangle

Equilateral Triangle

Three equal sides
Three equal angles, always 60°
Isosceles Triangle

Isosceles Triangle

Two equal sides
Two equal angles
Scalene Triangle

Scalene Triangle

No equal sides
No equal angles
How to remember? Alphabetically they go 3, 2, none:
  • Equilateral"equal"-lateral (lateral means side) so they have all equal sides
  • Isosceles: means "equal legs", and we have two legs, right?
      Also iSOSceles has two equal "Sides" joined by an "Odd" side.
  • Scalene: means "uneven" or "odd", so no equal sides.

What Type of Angle?

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

Acute Triangle

Acute Triangle

All angles are less than 90°
Right Triangle

Right Triangle

Has a right angle (90°)
Obtuse Triangle

Obtuse Triangle

Has an angle more than 90°

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