This one’s a right angled triangle, where one angle is always a right angle, so that's 90 degrees. All triangles have internal angles that add up to 180°, no matter the type of triangle.

Right-angled triangle. A right-angled triangle is a triangle where one of the angles is 90 degrees. A right angle is represented by a square, the side opposite the right angle. The longer side is ...

First, it has to be a shape with three sides---the "triangle" part. Second, one of the angles must be 90 degrees. That's it. With that, you can imagine a whole bunch of different triangles.

That means an angle cannot be greater than 360 degrees. Half of a full rotation is 180 degrees. This is represented as a straight line. One quarter of a rotation is 90 degrees. Another word for ...