Idea 11of 24Builds onEvery triangle has three angles
Name a triangle by its sides
How do a triangle's sides give it a name?
Today you'll discover
- three names from the sides
- what tick marks mean
- how to name a tipped-over triangle
Think firstSides 6 cm, 5 cm and 5 cm
How many of this triangle's sides are the same length?
Decide first, then press Next. Read the three lengths and look for tick marks.
A triangle with sides 6 cm, 5 cm and 5 cm; the two 5 cm sides get a tick mark each and a box names it isosceles. Then a triangle with all three sides 5 cm, ticked on every side, named equilateral, and one with sides 6, 4 and 5 cm, no ticks, named scalene. The last step shows a tipped-over triangle with sides 5 cm, 6 cm and 5 cm.
See the whole ideathe big idea and the key word, in one place
The big idea
Equilateral has three equal sides, isosceles has two, and scalene has none.
Compare themEquilateral: all three sides equal. Isosceles: two sides equal. Scalene: no sides equal. The same tick on two sides means those sides match.
Easy to get wrongTurning or tipping a triangle does not change its name. Measure the sides, whichever way it faces.
Key words
- equilateral triangle
- a triangle with all three sides equal
- isosceles triangle
- a triangle with two equal sides
- scalene triangle
- a triangle with no equal sides
Ready to use it?
- Name triangles by their sides.
- Mark equal sides with tick marks.