The angle should be measured with a protractor. The unit of measurement of angle is "degree", which is represented by the symbol "degree". Divide the semicircle into equal parts, and the angle of each part is degrees, which is recorded as "1".

The method of measuring angle with protractor;

(1) Put the protractor on the corner; Make the center point of the protractor coincide with the vertex of the angle.

(2) The zero scale line coincides with one side of the corner.

(3) Looking up from the zero scale coincident with the edge, the scale on the protractor opposite to the other side of the angle is the degree of this angle. Example 1: method of comparing angles: the size of an angle has nothing to do with the length drawn by both sides of the angle, but depends on the size of both sides. The bigger the fork, the bigger the angle.

(1) Line segments, straight lines and rays are all straight lines, and both line segments and rays are part of a straight line.

(2) A line segment has two endpoints, which can be measured; A ray has an endpoint and cannot be measured; The straight line has no end point and cannot be measured.

(3) Representation method: line segment AB, straight line AB, straight line L and ray AB.