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Lesson 5: Classifying geometric shapes

# Classifying shapes by line and angles types

Sal categorizes shapes based on their sides and angles.   Created by Sal Khan.

## Want to join the conversation?

• What do those two extra tiny lines mean on the triangle at ?
• This simply means that the two sides of the triangle are equal in length.
• Most of the triangles have multiple types of angles in them. How can you tell the name of the triangle if it has multiple degree angles?
• If one angle is a right angle than it's a right triangle, u don't have to look at the other angles. Same for obtuse angles. But for acute triangles all of the angles have to be acute for it to be an acute triangle.
• I know perpendicular means intersecting at 90*, and parallel means the two lines never intersect. What about the lines that intersect at more or less than 90*? Is there something that would explain that to me?
• keep in mind that if two lines intersect, and it is not a right angle, you will have a pair of acute angles and a pair of obtuse angles. Two lines intersecting will create 4 total angles
• Is that firstone a trapezoid? If so is it a right trapezoid?
• If a line is perpendicular it make a right angle?
• Perpendicular lines intersect at a 90 degree angle, so yes.
• could someone help me with this?
• I do not undstand
• what is a scalene triangle?
• a scalene is triangle where all 3 side are different, you can memorize this by thinking about how scales are never the same because they change so much
• how do i know if an angle is greater or lesser than a right angle
• A few extra.
acute less then 90°
right exactly 90°
obtuse between 90° and 180°
straight exactly 180°
And reflex between 180° and 360°