All courses Math I · G-CO.13 36 of 59
Construct an equilateral triangle, square, and regular hexagon inscribed in a circle.

Identify a regular polygon construction from its steps

Problem
Use the displayed construction state. Identify the regular polygon produced by the shown equal-step, diameter, or equal-radius construction.
Clean source or partial regular-polygon construction without the requested conclusion. Open full size
Your answer
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Hint

Count how many vertices the construction creates when you use the four endpoints of the two diameters.

Two perpendicular diameters create four equally spaced points on the circle. A regular polygon with four equal vertices on the circle is an inscribed square.

Solution walkthrough

01

Read the construction marks

\[\text{two}~\text{perpendicular}~\text{diameters}\]

The inspected prompt diagram shows one horizontal and one vertical diameter crossing at the circle's center.

02

Count the candidate vertices

\[2~\text{endpoints}~\text{per}~\text{diameter};~2~\text{diameters}~\text{give}~4~\text{circle}~\text{points}\]

Each diameter ends at two points on the circle, so the construction supplies four distinct vertices.

03

Use the right-angle spacing

\[360/4~=~90~\text{degrees}~\text{between}~\text{adjacent}~\text{points}\]

Perpendicular diameters divide the circle into four equal quarter-turns. Connecting adjacent endpoints makes four equal chords and four right angles.

04

Name the constructed polygon

\[\text{inscribed}~\text{square}\]

A regular four-sided polygon whose vertices lie on the circle is an inscribed square.

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Another way

  1. Recognize that joining the endpoints of perpendicular diameters always forms an inscribed square.

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Common mistake

Do not answer rectangle merely because opposite sides would be parallel. The perpendicular diameters create equal quarter-arcs, so all four side chords are equal.

Annotated answer diagram marking the completed regular polygon, central angle, invariant, or comparison.
polygon: inscribed square