# Chords in Circles: A Paper Folding Activity

Are you looking for a fun, hands-on activity to teach your geometry students about chords in a circle? Look no further! Paper folding is an inexpensive and creative way to help your students understand the concept quickly. This low-prep activity is perfect for showing them that two points on a circle determine a chord, as well as exploring some properties of chords. With just a few pieces of paper, some markers, and our step by step instructions, you'll be teaching chords in circles with ease. Get ready for your students to have fun as they learn-- let's fold!

To get started, you will need the following supplies:
• Tracing Paper
• Ruler
• Compass
• Marker or Pen
Don't forget to scroll all the way to the bottom to grab the student instruction sheet!

## Chords in Circles Activity 1

First, draw a circle on tracing paper or thin paper using a compass.  Remember to include the center!

Use a straightedge to draw two radii anywhere on the circle.

Use a straightedge to mark a distance shorter than the radii.  Choose a length and mark it on one radius.  Then, mark the radius at the same length to make two congruent segments.  Remind students to measure carefully.

Now, at the point you marked on each radius, fold a line perpendicular to the radius.  Students sometimes have trouble folding straight.  They will have more success with sharp creases on their folds.

Mark the endpoints of one chord A and B and the endpoints of the other chord C and D.

Now, ask students what they notice about the lengths of the chords.  They should notice that the lengths of the chords are the same.

## Chords in Circles Activity 2

Begin again with a circle on thin paper or tracing paper.  Use a compass and remember to draw the center!

Then, use a straightedge to draw two chords of different lengths.  Do not draw a diameter.

Use the ruler to mark the center of each chord.  Then, fold the perpendicular bisector of each chord.  This can be tricky, so fold carefully.

Now, ask students what they notice about the perpendicular bisectors.  Students should notice that the perpendicular bisectors meet at the center of the circle.

Paper folding is a great way for geometry students to get hands on practice so they can understand theorems.  Circle theorems can seem abstract, but this paper folding activity will help students see the properties of chords in circles!