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