Joe uses the following steps to construct a perpendicular line through a point C on a line segment:

Step 1: From point C, draw an arc intersecting the line segment in points A and B.
Step 2: Use a straightedge to draw an arc from point A, one above and the other below the line.
Step 3: Without changing the compass width, draw two arcs from point B, above and below the line segment.
Step 4: Label the point of intersection of the arcs above the line segment as Q and below the line as R.
Step 5: Using a straightedge, join points Q and R.
Part A: Which is the first incorrect step?

Question

Joe uses the following steps to construct a perpendicular line through a point C on a line segment:

Step 1: From point C, draw an arc intersecting the line segment in points A and B.
Step 2: Use a straightedge to draw an arc from point A, one above and the other below the line.
Step 3: Without changing the compass width, draw two arcs from point B, above and below the line segment.
Step 4: Label the point of intersection of the arcs above the line segment as Q and below the line as R.
Step 5: Using a straightedge, join points Q and R.
Part A: Which is the first incorrect step?

anonymous · Answer

Part B: Using complete sentences, explain your answer for Part A.
Part C: Explain why a compass works for the construction done by Joe.