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### Course: Geometry (all content)>Unit 2

Lesson 8: Sal's old angle videos

# Angles (part 3)

Angles formed when a transversal intersects parallel lines. Created by Sal Khan.

## Want to join the conversation?

• Why is this video so pixelated?
the whole time
• It's because it's an old video which does not have very high quality. That's why it's under "Sal's old angle videos."
• What are interior angles and exterior angles?
• Does a transversal have to be a line segment or a line or can it be both ?
• I believe it can be a line segment or a line. Although all of the definitions I've found (Wikipedia and Wolfram Mathworld) - say "Line" and never "Line Segement".
• He explained what transversal is... But I still don't get it. Can anyone explain please?
(1 vote)
• In my example here, there are two parallel lines (shown by the >) and a third line going straight, and intersecting them both. The third line is called the transversal.
-----------|----->--------
-----------|----->--------
The video after this one is really helpful for explaining this.
• On that diagram how do we get cointerior angles?
• The angle marked in yellow between the green and purple lines is cointerior with the angle marked in magenta between the cyan and purple lines.

The angle marked in yellow between the cyan and purple lines is cointerior with the angle marked in orange between the green and purple lines.

Cointerior angles are the angles formed between the transversal and the parallel lines, which are on the same side of the transversal line. This means that there are two pairs of cointerior angles.
(1 vote)
• can you alter a triangle to equal more than 180 degrees?
(1 vote)
• No. You need to make the sum of the interior angles equal to 180 or else it wouldn't be a triangle.
• how does a triangle add up to 180 degrees
(1 vote)
• Draw a square. Draw a diagonal line across the square, from one corner to the other. See how you made two triangles, that are each half of the square? If the square is 360, then half must be 180.
• What is the angle of a circle with a diameter of 10?
(1 vote)
• 360 degrees. The number of degrees never changes depending on the diameter. It really depends on what the shape is.