ACT Preparation / Unit 13 ACT 1209 short lesson, about 20 seconds
Triangle Types
Captions available
The idea
By sides, a triangle is scalene with no equal sides, isosceles with two equal sides, or equilateral with three. By angles, it is acute, right or obtuse.
In practice
An equilateral triangle has three 60° angles.
Where people slip
The two kinds of name combine: a right isosceles triangle has angles of 90°, 45° and 45°.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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