A right angle is a special corner — when two lines meet perfectly straight up to each other. The corner of a sheet of paper is a right angle. So is the corner of a window, a door, a book.
A right angle is 90°.
How to recognise one
Take a piece of paper. The corner is a perfect right angle.
Place the paper corner against the corner of the shape you're checking.
If the two edges line up exactly, it's a right angle.
Right angles in shapes
Shape
Right angles
Square
4
Rectangle
4
Right triangle
1
Equilateral triangle
0
Regular pentagon
0
L-shape and other "corners in/out"
Look at this L-shape:
.███.
.███.
.█████
.█████
It has 6 right angles: 3 outer + 3 inner corners.
When the shape goes "in" — that inner corner is also a right angle (just facing the other way).
