# Geometry - Arcs and Chords

When it comes to the shapes you learn about in Geometry, the circle can be the trickiest. You don't have all those nice straight lines to work with and instead have curves, a whole different set of formulas, and pi. We saw some of these differences at work on the video on Spheres.

Measuring the side of a square is one thing but what do you do when you want to measure the length of an arc? An arc of a circle is basically any connected part of the circle's circumference and finding the measurement of an arc is directly related to the measurement of the central angle for that arc. In today's free Geometry video on Arcs and Chords, you'll learn how to calculate the measurement of both an arc and a chord. A chord is a line segment whose endpoints lie on the circumference of the circle.  The four lectures on the video will give you a great understanding of Arcs and Chords. Just be sure to click the forward button the left of the time stamp to move to the next lecture on the video.