Copy segments and angles 1
Segment \(\overline{AB}\) has length \(2.35\,\text{cm}\), and ray \(\overrightarrow{P_0X}\) is given.
Describe how to use one unchanged compass opening to mark points \(P_1,P_2,P_3,P_4\) in order on the ray so that each consecutive segment is congruent to \(\overline{AB}\). Your description must state where the compass is centered for each new point.
Then find \(P_0P_4\) and explain, using the copied segments, why \(P_2\) is the midpoint of \(\overline{P_0P_4}\).
Hints
- The compass opening should stay fixed after it is matched to the source segment.
- Each new endpoint becomes the center for the next transfer.
- Compare how many copied intervals lie on each side of \(P_2\).
Solution
1. Set the compass opening to \(AB\) and do not change it.
2. Center the compass at \(P_0\) and mark \(P_1\) on the ray. Then center it successively at \(P_1\), \(P_2\), and \(P_3\) to mark \(P_2\), \(P_3\), and \(P_4\).
3. The four consecutive copied segments each have length \(2.35\,\text{cm}\), so \(P_0P_4=4\cdot2.35=9.40\,\text{cm}\).
4. Each of \(P_0P_2\) and \(P_2P_4\) consists of two copied segments, so both equal \(4.70\,\text{cm}\). Therefore, \(P_2\) is the midpoint.
Answer
Keep the compass set to \(AB\). Center successively at \(P_0,P_1,P_2,P_3\) to mark the next point on the ray each time. Then \(P_0P_4=9.40\,\text{cm}\), and \(P_2\) is the midpoint because \(P_0P_2=P_2P_4=4.70\,\text{cm}\).
