A preliminary understanding of 1 and angle
The (1) angle consists of a vertex and two sides.
(2) Angle drawing method: Starting from one point, draw two straight lines in different directions with a ruler.
(3) The size of the angle is not related to the length of the side, but related to the size of both sides of the angle. The bigger the angle is, the bigger the angle is, and the smaller the angle is.
2. A preliminary understanding of right angles
(1) Judgment method of right angles: Compare right angles on a triangular ruler (vertex to vertex, one side to one side, and then see if the other side is coincident).
(2) Method of drawing a right angle: first draw a vertex, and then draw a straight line from this point. Align this point with the right-angled vertex on the triangular ruler and align a right-angled edge with this line. From this point, draw a line along the other right-angled side of the triangular ruler. Finally, mark the right angle sign.
(3) Acute angle is less than right angle, obtuse angle is greater than right angle: acute angle.