By the end of this section you should be able to: ● complete constructions 5 and 6
We have already looked at construction 5 in Section A, Unit 3. We will now look at an alternative method of carrying out this construction, using only a compass and a straight edge.
Construct a line parallel to a given line, using a compass and a straight edge
1
Start by drawing a line m and a point P (not on m). Choose a point Q anywhere on the line m and draw QP.
2 5
Place the compass point on Q and draw an arc that crosses QP and line m. Label the points of intersection A and B as shown.
Using the same compass setting, place the compass point on P and draw an arc on QP. Label point C, as shown.
C P A Q 3 m
With a compass width |PC|, place the compass point on C and draw an arc such that it intersects the first arc, as shown.
Label the intersection of these arcsD. C P A Q B D m A Q B P D m C 4 Q B m Draw PD. This line is parallel to line m. P