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 at1:05?(40 votes)
- 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?(6 votes)
- 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.(2 votes)
- If a line is perpendicular it make a right angle?(6 votes)
- 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?(4 votes)
- 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(5 votes)
- um l think khan academy is the best and nice but l had one be is what 3x10 is 30 but that is wrong l put wrong
l think so hard l can not do it(4 votes)
- He is showing some exercises that he is using, where to access them?(3 votes)
- Here are links to the two practice exercises that are part of this lesson. These are the updated versions of the ones you see in the video, so they are not exactly the same:
The exercises that you see in the video are from an older version of the website, which is why the format is a bit different. The old exercises are no longer available.(1 vote)
Which side is perpendicular to side BC? So BC is this line segment right over here. And for another segment to be perpendicular to it, perpendicular just means that the two segments need to intersect at a right angle, or at a 90-degree angle. And we see that BC intersects AB at a 90-degree angle. This symbol right over here represents a 90-degree, or a right angle. So we just have to find side AB or BA. And that's right over here. Side AB is perpendicular to side BC. Let's do a few more of these. Put the triangles into the correct categories, so this right over here. So let's see. Let's think about our categories. Right triangles-- so that means it has a 90-degree angle in it. Obtuse triangles-- that means it has an angle larger than 90 degrees in it. Acute triangles-- that means all three angles are less than 90 degrees. So this one has a 90-degree angle. It has a right angle right over here. So this is a right triangle. This one right over here, all of these angles are less than 90 degrees, just eyeballing it. So this is going to be an acute-- that's going to be an acute triangle. I'll put it under acute triangles right over there. Then this one over here, this angle up here, this is-- and we can assume that these actually are drawn to scale, this is more open than a 90-degree angle. This is an obtuse angle right over here. It's going to be more than 90 degrees. So this is an obtuse triangle. Now, this one over here, all of them seem acute. None of them even seem to be a right angle. So I would put this again into acute-- acute triangles. This one here clearly has a right angle. It's labeled as such. So we'll throw it right over here. And then this one, this angle right over here is clearly even larger. It has a larger measure than a right angle. So this angle right over here is more than 90 degrees. It's going to be an obtuse angle. So we will throw it into obtuse-- obtuse triangles. So we got two in each of these. And let's check our answer. We got it right.