# Construct a pentagon/construction

*Given a circle, inscribe a regular pentagon.*

## Contents

## Construction: Inscribed Pentagon

Although we generally consider the circle as given, in theory we should always start with two given (arbitrarily chosen) points.

### Step 0

Given points A and O, draw circle O with radius AO and diameter AA'. Let AO be 1 unit.

### Step 1

Construct the perpendicular bisector of AA' and find one intersection with circle O; call this S.

### Step 2

Construct the perpendicular bisector of SO and find its intersection with line SO; call this M.

### Step 3

Draw a circle M with radius OM.

### Step 4

Draw a line through A' and M. Find its intersections with circle M; call these P and Q.

### Step 5

Draw (two) circles with center A' and radii QA' and PA'. Find their intersections with circle O; call these B, C, D, and E.

### Step 6

Draw lines AB, BC, CD, DE, and EA.

*I say the figure ABCDE is a regular pentagon.* QEF.