Foundation and Higher · constructions

Do you know the difference between these two constructions?

perpendicular bisector
vs angle bisector

first, the word itself —

Bisector

Bi — means two

sector — means parts

construction 1 of 2

Perpendicular
bisector

1. Draw a line segment AB.

2. Compass arc from A.

3. Same arc from B.
Keep your compass the same distance apart.

4. Join where the arcs meet.

✓ Cuts AB exactly in half at 90°.

Now the second one…

construction 2 of 2

Angle
bisector

1. Start with the angle at V.

2. Arc from V crosses both rays.

3. Two more arcs from each crossing.

4. Join V to where they meet.

✓ Cuts the angle exactly in half.

the difference

Perpendicular bisector
bisects a LINE

Angle bisector
bisects an ANGLE

Students always mix these up —
make sure you don't.

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