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Acute Right and Obtuse Angles

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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
Title:
Acute Right and Obtuse Angles
Description:

The difference between acute, obtuse and right angles

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Video Language:
English
Duration:
05:32

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