Bahan Ajar Matematika SMP Kelas 7 Berbahasa Inggris.

Using Compass And Ruler To Draw Angles 60° And

90°

Drawing Angle 60° Using Compass and Ruler

Step-by-step Instructions :1. Draw a line segment which will become one side of the

angle. (Skip this step if you are given this line.) The exact length is not important. Label it PQ. P will be the angle's vertex.

2. Set the compass on P, and set its width to any convenient setting.

3. Draw an arc across PQ and up over above the point P.

4. Without changing the compass width, move the compass to the point where the arc crosses PQ, and make an arc that crosses the first one.

5. Draw a line from P, through the intersection of the two arcs.

6. Done. The angle QPR has a measure of 60°.

And then check with a protractor.

Drawing Angle 90° Using Compass and Ruler

Step-by-step Instructions :1. Start with a ray with endpoint A. The right angle will have A as its

vertex.

2. Pick a point not on the given line, about 6 cm from one of its endpoints. Its exact location is not important. Label it D.

3. Set the compass on point D and set its width to the chosen endpoint.

4. Draw an arc that crosses the given line and extends over and above the chosen endpoint. (If you prefer, draw a complete circle.)

5. Draw a diameter through D from the point where the arc crosses the given line.

6. Draw a line from the chosen endpoint to the endpoint of the diameter line.

7. Done. The last line drawn is perpendicular to the given line.

And then check with a protractor.