Occasionally you may want to create an angle of fixed measure — for example, an angle that measures exactly 33°. While you could create an angle by measuring three points and dragging them until they form an angle of 33°, this angle would not be constructed to be fixed at 33°. Dragging it again would change it from its current magnitude to some other magnitude.
To fix an angle in Sketchpad, you need to construct the angle in such a way that dragging cannot change its magnitude. For an arbitrary angle, the easiest way to do this is with the Transform menu.
| 1. | Use the Point tool to to construct two points, A and B, in your sketch. |
| 2. | Select point A and choose Transform | Mark Center. Point A is marked as the center of future rotations and dilations. |
| 4. | In the dialog box, enter the fixed angle by which you want to rotate. Click the Rotate button to confirm your choices. |
| 5. | Sketchpad constructs point B' as the rotated image of B by your requested angle. Even if you drag A, B, or B', Sketchpad will maintain this angle’s magnitude, because you’ve defined B' to be the rotated image of B by this angle. |
You can now construct rays or segments connecting A to B and to B' to incorporate the fixed angle into your sketch.
How to Construct a Segment of Fixed Length
How to Construct Congruent Angles
