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Copying a Line Segment
Constructing a 30° Angle
Constructing a 60° Angle
Finding the Center of a Circle
Constructing Circumcenter of a Triangle
Constructing an Equilateral Triangle
Constructing a Perpendicular Bisector of a Line Segment
Constructing a Perpendicular at the Endpoint of a Ray
Constructing Tangents Through an External Point

Constructing Tangents Through an External Point

(This demonstration shows how to make a copy of a line segment using only a compass and straight edge.)

Step by Step Instructions
  1. Mark a point R that will be one endpoint of the new line segment.
  2. Set the compass point on the point P of the line segment to be copied.
  3. Adjust the compass width to the point Q. The compass width is now equal to the length of the line segment PQ.
  4. Without changing the compass width, place the compass point on the point R on the line you drew in step-1.
  5. Without changing the compass width, draw an arc roughly where the other endpoint will be.
  6. Pick a point on the circle that will be the other endpoint of the new line segment.
  7. Draw a line between points.
  8. Done. The new line segment is equal in length (congruent to) the line segment |PQ|.

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