Bisectors and perpendiculars

Halve segments and angles; drop and raise perpendiculars.

• Perpendicular bisector Two equal circles; join their crossings
• Midpoint of a segment The perpendicular bisector meets the segment at its middle
• Perpendicular at a point on a line Mark equal distances either side, then bisect
• Perpendicular from a point to a line Circles about two points of the line through P
• Bisect an angle Equal marks on both arms, then two equal circles