2. Know boxers and rounded corners. Flat angle: the two sides of the angle are on the same straight line (like a straight line), and the flat angle is equal to 180, which is equal to two right angles. Fillet: two sides of an angle coincide (like a ray), and the fillet is equal to 360, which is equal to two right angles and four right angles.
3. Classification of angles: angles less than 90 degrees are called acute angles; An angle equal to 90 degrees is called a right angle; An angle greater than 90 degrees and less than 180 degrees is called an obtuse angle; An angle equal to 180 degrees is called a right angle; More than 180 degrees and less than 270 degrees is called the optimal angle (this is a supplementary content); An angle equal to 360 degrees is called a fillet.
4. Consciousness. Divide the circle into 360 parts on average, and the angle of 1 part is called 1 degree, and recorded as 1 degree. 1 degree is usually used as the unit for measuring angles.
5. Know the protractor. The protractor divides the semicircle into 180 parts, and one part represents 1 degree. The protractor has a center point, a zero scale line, an inner scale line and an outer scale line.