Ruler Drawing 20 10-4- 19 I. About the use of ruler drawing and accurate drawing as required. Don't use the scale of the ruler, the existing triangle and the angle of the protractor. Second, several basic drawing methods 1, draw a line segment equal to the known line segment as shown in figure 1, MN is the known line segment, and accurately draw a line segment AC equal to MN with a ruler and compasses. Step: 1, draw AB, 2, then measure the length of the line segment with, and intercept AC = Mn on AB, then the line segment AC is the line segment to be drawn. 2. Draw an angle equal to the known angle as shown in Figure 2, and ∠AOB is the known angle. Try to draw ∠ A ′ O ′ B ′ equal to ∠ AOB accurately with compasses and straightedge according to the following steps. Steps: 1, draw the ray O'A'2, draw an arc with the O point as the center and the appropriate length as the radius, pass through OA at C point, pass through OB at D.3 point, and take the O' point as the center. When the previous arc is at d' .5, draw an o' b' line through point d'. ∠ A' o' b' is the angle to be drawn. 3. Draw the definition of perpendicular bisector's known line segment: The straight line on a line segment is called the perpendicular bisector (or the median vertical line) of the line segment. As shown in the figure, the line segment AB is known and the vertical line is drawn. Step: 1. Draw an arc with point A as the center and a length greater than half of AB as the radius; 2. Draw an arc with the same length as the radius with point B as the center; 3. Record the intersection of two arcs as C and D respectively, and connect CD, then CD is the middle vertical line of segment AB; 4. Draw an angle bisector, and divide an angle with a ruler and compasses. It is known that ∠AOB as shown in Figure 3 is calculated as: ray OC, Make ∠ AOC = ∠ BOC step: on 1, OA and OB, respectively intercept OD and OE, so that OD = OE 2, respectively take D and E as the center, and the length greater than the radius is an arc. In ∠AOB, two arcs intersect at C3 to form ray OC, which is the required ray. 5. Draw a straight line perpendicular to the known straight line (1). Draw a straight line perpendicular to the known straight line, as shown in the figure, with point A above and point A as a straight line, so ⊥ Exercise: 1, with point A as the center and appropriate length as the radius, draw an arc intersecting point B and C2 with a radius greater than BC. AD means that the sought straight line (2) passes through a point outside the straight line to make a straight line perpendicular to the known straight line 1, and draws an arc with point A as the center and the length greater than the distance from point A as the radius to pass through B and C2, respectively with point B and point C as the center and the radius greater than BC as the center, and makes an arc on the other side with the intersection point D3 to connect AD. Then, AD is the sought linear motion-65438+. As shown in the figure below, find a line segment to make its length equal to AB+2cd.2 As shown in the figure, ∠A and ∠B are known, and find an angle to make it equal to ∠ A-∠ B. 。

3. Make △ABC and its inscribed circle as required. (1) is expressed as △ABC, so BC=, AC= and AB= (2) are all inscribed circles of △ABC.

4. Draw an isosceles △ABC as shown in the figure, so that the bottom BC= and the high AD=

5. As shown in the figure, ∠AOB and M and N are known. Let's find point P, so that the distances from both sides of point P to ∠AOB are equal, and the distances from two points to M and N are also equal.

Exercise 2 1. Know that three sides are triangles, and that three sides of a triangle are A, B and C.2. We know the two sides of a triangle and their included angles, so we can calculate it as a triangle. We know that the two sides of a triangle are A and B, and the included angle between these two sides is ∠a, so we can calculate it as a triangle. We know that the two angles of a triangle are ∠a ∠β, so we can calculate it as a triangle. 4. Given two angles of a triangle and the opposite side of an angle, find a triangle. It is known that the two angles of a triangle are ∠a ∠β, and the opposite side of ∠a is ∠a. Find this triangle. 5. Knowing the right-angled side and hypotenuse, find a right-angled triangle with the right-angled side length of C and the hypotenuse length of C, and find this triangle for practice. (Requirements: write what is known, work hard and keep the trace) Known: work hard: 2. Drawing with a ruler: Please make a diamond with line segments and diagonal lines (requirements: write what is known, what is hard and what is concluded, draw with a ruler and compasses, keep drawing traces, and don't write methods and proofs).

Work: Conclusion: 3. As shown in the figure, in △ABC, ∠ BAC = 2 ∠ C. (1) makes the bisector AD of the inner corner of △ABC in the figure; (Requirements: Draw with a ruler and a ruler, and keep traces of drawing, and do not write proof) (2) Write a pair of similar triangles and explain the reasons. Find an uncalibrated ruler and compass and draw the following figure: 1. Make a line segment equal to a known line segment. 2. Make an angle equal to a known angle. 3. Take the line segment as the edge. Make an angle equal to a known angle. 4. Make the midpoint of the line segment. 5. Make a bisector of an angle. 6. Do a little on a straight line perpendicular to the straight line. 7. Do something outside the straight line (line segment) perpendicular to the straight line (line segment). 9. Do something outside the straight line (line segment) parallel to the straight line (line segment) 10. Make the bisector of line segment 6544. Making a circle is equal to the known circle 13. Make a triangle with "five centers" 14. Make an angle equal to 30 15. Make an isosceles right triangle and a regular triangle 16. Make a diamond 17 with an angle of 60. Make a side length. My world, my world is a fan-shaped teacher Zheng with a central angle of 60+00-4-1948143919.