Constructing a 90°, 45° or 22.5° Angle
Rule
Instructions for Constructing Angles
- 1.
- Draw a straight line and make a point on the line.
- 2.
- Put the point of the draft compass on and make an arc that intersects the line on both sides of .
- 3.
- Call the intersections and .
- 4.
- Put the point of the draft compass on and make a small arc above .
- 5.
- Without changing the distance between the legs of the draft compass, do the same thing on . Make sure the two arcs intersect.
- 6.
- Draw a line from the point through the point where the two small arcs intersect. This is a ° angle.
Constructing a Angle
When you need to find an angle that is half of another angle, you always use the bisection technique. When you construct a ° angle, you just bisect a ° angle. You simply make a cross, midway between the two sides of the angle, with your draft compass, and draw a line from the vertex through this cross. The two new angles are both °, because .
Constructing a Angle
Once again, you need to find an angle that is half of another. For that reason, you can just use the bisection method one more time. So when you construct a ° angle, you just bisect a ° angle. You simply make a cross midway between the two sides of the angle with your draft compass, and draw a line from the vertex through this cross. The two new angles are both °, because .
