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In this video, I really wanted to introduce
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you to some terminology for some basic angle types
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and terminology. I wanted to introduce you to are
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acute angles, right angles, and obtuse angles.
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I think when we go through these,
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it will be pretty self-explanatory.
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And an acute angle is an angle --
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let me just draw them first
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then you might,
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you might,
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it might start to make sense.
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So an acute angle
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will look something like that.
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I draw two rays
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coming from a common point.
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I could also --
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so the acute angle could be this angle right over here.
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I could also draw an acute angle;
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maybe an angle that is formed from an intersection of two lines,
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so this angle would be acute,
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and so will this angle.
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They're both acute angles.
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We are going to see acute angles as ones
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that are --
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that since I haven't defined right angles yet.
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They are narrower,
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so we are going to see that they are
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smaller than right angles.
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Right angles are when the rays
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or the lines are going, oh
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I guess, I don't want to use the word "right"
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in my definition.
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They are kind of
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if one is going horizontal
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then the other one will be going vertical.
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so let me draw with rays first
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so the right angle
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this one is going from the left to the right
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and the other ray is going from the bottom
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to the top
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this angle right over here
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is a right angle
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and I could label it like that
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but as a traditional angle
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but the general,
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the general convention for labeling right angles
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is to put a little,
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a kind of a half of a box over there.
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That tells me that this is a right angle
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or, that if this is going left to right
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this is going perfectly top to bottom
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that this is a no way kind of
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that this is a completely,
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I guess the best way to think about it
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why it's called right
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is that this ray is completely upright
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compared to this ray over here
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let me draw with some lines
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if I have one line like this
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and I have another line like that
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a right angle over here
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actually all of these would have to be
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right angles
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it would mean that this line
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is completely,
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if this line were the ground,
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this line is completely upright
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relative to this line over here.
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so either these,
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so that is what a right angle means
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so now that we defined right angle
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I can give you another definition for acute angle
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so an acute angle has a measure
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or it's smaller than a right angle
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so you learn about radients and degrees
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which are different ways to measure angles
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so you'll see that a right angle
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can be measured as 90 degrees
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this over here is less than 90 degrees
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so this is less than 90 degrees.
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and one way to conceptualize this is
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that this angle,
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it's opening is smaller
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it's more narrow,
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it's lines are,
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you would have to rotate one line
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less to get to the other line
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then you would over here.
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here, you would have to move
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all the way over there
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here you only have to move it a little bit
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so the acute angle is less than a right angle
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so you might imagine already
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what an obtuse angle is
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it is greater than a right angle
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so let me draw a couple of examples
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of obtuse angles
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so an obtuse angle might look like
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let me get it a little clearer
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might look like that
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if it was a right angle,
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then this line over here
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would be,
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would look something like that
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it would be completely upright
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relative to this, if this were the ground.
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but we don't see that
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this orange ray over here is actually
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opened out wider
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it's opened up wider
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so it is obtuse.
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it is obtuse
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so this kind of comes from the actual
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everyday meaning
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acute means very sharp or very sensitive
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obtuse means not very sharp or not very sensitive.
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you could imagine this looks like a sharp point
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or it's, it's not opening up much.
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so maybe it's more sensitive to
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you know, relative to other things
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I don't know, just trying to make connections
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This is less sensitive
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It's all big and open
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It won't be able to notice things that are small
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or maybe that is not an appropriate analogy
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but one way to think about it
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it's kind of open up wider,
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or it's bigger than a right angle
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it's larger than 90 degrees
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larger than 90 degrees
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if you measure it
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you would have to rotate this ray more to
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get to this other ray
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than you would if you had right angles
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and definitively a lot more if they were acute angles.
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If I were to draw this with lines,
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which of the angles are obtuse and
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which are acute?
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Well the way I drawn them right over here,
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these two over here are acute
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are acute
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and then these over here are going to be
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obtuse
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so this one
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and this one
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these are both obtuse angles
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and I actually drew them up here as well.
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This one and this one are going to be
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obtuse
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so very simple idea
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if one line
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or if one ray is relative to the other one
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is straight up and down
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versus left to the right
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or is completely upright
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then we're talking about a right angle
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if they are closer to each other
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if you had to rotate them less
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you're talking about a acute angle
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if you had to rotate them more
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you are talking about an obtuse angle
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and I think if you look at them visually
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it's pretty easy to pick out