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Course: 8th grade foundations (Eureka Math/EngageNY)>Unit 2

Lesson 1: Topic A: Foundations

Classifying shapes by line and angles types

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

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• 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.
• 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
• could someone help me with this?
• So an obtuse triangle has only 1 obtuse angle?
• yes it is impossible to have an obtuse triangle with more than one obtuse angle.
Since an obtuse angle is more than 90 degrees then the other 2 angles can't be more than 90 since the overall degrees in a triangle is 180 and 90 + 90 = 180 so then it wouldn't be possible to have 2 obtuse angles
Hope this helped!