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Angle Copy and Bisector

Copying Angles

Copying an angle is a fairly simple construction. Follow these steps to copy the given angle.
  1. Select the compass tool. Click on point A and then point C. Center your circle on point A by clicking point A again.
  2. Use a point to mark the intersection of your circle with the bottom ray of your angle. This should be point F.
  3. Select the compass tool again. Click on point A and then point C. This time, center your circle on point D by clicking point D.
  4. Use a point to mark the intersection of this new circle with your ray that starts at point D.This new point should be point G.
  5. Select the compass tool one last time. Click point C and then point F. Center this circle at point G.
  6. Use a point to mark the intersection of your new circle with the circle centered at point D.
  7. Draw a ray from point D to the intersection point you just marked.
You've now copied an angle! If you click and drag point C, you should see your new angle below move as well. This is a way to test your construction.

Angle Bisector

An angle bisector cuts an angle into two congruent angles. We are going to construct an angle bisector of the angle below.
  1. Select the compass tool. Click point A, then click point B. Center your circle at point A by clicking point A.
  2. Mark the intersection of your circle with the bottom ray of your angle. This should be labeled point D.
  3. Select the compass tool. Click on point B, then click point D. Center this circle at point B.
  4. Select the compass tool again. Click point B, then click point D. This time, center the circle at point D.
  5. Mark the intersection of these two circles with a point. This point should be in the interior of your angle and should be called point E.
  6. Use the ray tool to make a ray starting at point A and going through point E. This ray is your angle bisector.
Congrats! You just bisected an angle. When you move point B, you should see your whole construction move with it. The key is, that the ray from D to E should always be in the middle of your angle.