An angle of 90 degrees is called a right angle, an angle greater than 90 degrees is called an obtuse angle, and an angle less than 90 degrees is called an acute angle, so a picture with a graphic angle of 90 degrees is called a right angle, a picture with a graphic angle less than 90 degrees is called an acute angle, and a picture with a graphic angle greater than 90 degrees is called an obtuse angle. A right angle is an angle equal to 90 degrees, and an acute angle is an angle less than 90 degrees and greater than zero. The obtuse angle is greater than 90 degrees and less than 180 degrees.
Triangle angle classification
Three internal angles of a triangle are all acute angles, which is called "acute triangle";
One of the internal angles is a right angle, which is called a "right triangle";
One of the internal angles is obtuse, which is called "obtuse triangle";
An equilateral triangle is called an isosceles triangle;
A triangle with three equilateral sides is called a regular triangle or an equilateral triangle.