First, acute angle, right angle and obtuse angle.

Second, boxers, rounded corners

Third, the vertex angle

Fourth, the same angle, internal angle.

If classified by triangle, there are three kinds: acute angle, right angle and obtuse angle.

Right angle 180, fillet 360.

If the sum of two angles is equal to 90, they are said to be complementary angles.

If the sum of two angles is equal to 180, they are said to be complementary angles.

If two straight lines intersect, two sets of diagonal angles are formed at the intersection.

If two straight lines are parallel, there are congruent angles and internal angles.

These are all speaker types that must be fully mastered in the first year.