If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# CA Geometry: Circle area chords tangent

71-75, area, chords, tangents of circles. Created by Sal Khan.

## Want to join the conversation?

• What is the proof of ""
• The explanation by Jack Li is correct. Here is a video on youtube with a diagram that might make it clearer. http://www.youtube.com/watch?v=TfRiX7nnM44
(1 vote)
• I can't seem to find the video with problems 75-80. Could someone give me the link, please?
Thank you!
• I think when he said 80 problems, he was also including the example problems in the first videos of this series.
(1 vote)
• Do you have a video explain how to measure the length of a chord?
• Is there a video where Sal proves this? Thanks
• How do you remember which side is 2x and root 3x?
• how to tell if whether each polygon is inscribed in or circumsribed about the circle
• the first problem answer was (A)5 because we just have to find the X value and the answer would be just 5 not 5 square root of 2.
• yes, eight years later, I am here, I believe he meant to have one of the variables as y, so they differ
(1 vote)
• what is an arc of a circle?
• An arc is a segment of the circle's curve. More info can be found at: Language and notation of the circle at around .
(1 vote)
• how do i find tangent ratios?