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volunteer
over the change in X.
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2 minus X1.
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volunteer
And we know, and we can say
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volunteer
that it's F(X2)
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volunteer
minus FOX1 because Y1 is just equal to F of X1.
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volunteer
over X2.
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volunteer
minus X1
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volunteer
right? So now the question becomes
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volunteer
um, what is F of X2.
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volunteer
And how is it related
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volunteer
to X1? Can we use X1 to approximate F of X2 if we don't know what F of X is.
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volunteer
right? Like the only, the only information we have about FFX
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volunteer
is the point X1F of X1.
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volunteer
and that it's occur and then we have a tangent line.
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volunteer
That's the only information we have about the function F
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volunteer
Um, and knowing that we want to know, is there, is it possible to find the value F of X2.
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volunteer
OK.
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volunteer
So going back to this equation, we say FX2 what is is equal to FFX1, which is just, you know, Y1
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volunteer
We're saying plus some uh delta X
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volunteer
times
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volunteer
the slope
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volunteer
which really is just some kind of
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student
ok ok
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volunteer
right, which really this, this is actually just some kind of like error function.
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student
ohhh
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volunteer
right? Because we know that um
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volunteer
that
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volunteer
Y2 cannot equal F of X2.
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volunteer
because the definition of a tangent line
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volunteer
means that it only intersects the function at one point.
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volunteer
So by definition, Y2 can't, there can't be a second
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volunteer
point
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volunteer
that the tangent line touches on the function because by that point, it wouldn't be a tangent line anymore. It'd be a secant line.
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student
yeah
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volunteer
right
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volunteer
So, um
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volunteer
and what what happens is, is that if you can approximate
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volunteer
this delta X, if you take whatever step you have, you would find that, um, let's say F of X2
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volunteer
is equal to Y1, right? The, the point we know about the, the height of the point we know about, plus some
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volunteer
uh
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volunteer
I'm sorry, let me do that again. This is actually
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volunteer
not Y2. This would be Y1, right? So you say FFX2 because we know what F of X1 is in relation to why we can approximate say FFX2 is equal to Y2, let's say plus some error value.
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volunteer
right? Cause we know Y2 can't equal XF X2.
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volunteer
but if we, depending on how big our delta X is, we know that we can, um, kind of approximate
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volunteer
this value. This in all this right here is just an approximation.
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volunteer
right? Because we want to know what is this error value?
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volunteer
And we say it's an error value because we know, um, if you look back at the graph
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volunteer
right, we have Y2 here.
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volunteer
and this is F of X2, and you see there's this gap here.
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volunteer
right?
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volunteer
And that gap
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volunteer
I'm sorry, that's not a plus, it should be a minus then.
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volunteer
Uh
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volunteer
I guess it doesn't really matter
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volunteer
Yeah, it's, it's a minus
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volunteer
I guess the sign doesn't really matter because it could just be a negative value.
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volunteer
But basically, we want to know what is um
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volunteer
what is this error value
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volunteer
right? What is this gap between Y2 and X2.
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volunteer
And the, and the problem becomes if this gap
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is too big
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then we really have no idea what F of X2.
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is.
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right? Approximation could be way off.
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volunteer
And this is, this happens when um
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volunteer
this gap between X2 and X1. By the way, I didn't, I didn't explain this, but Delta X is just equal to um the difference between two points of X. So it'll be X2 minus X1, or it could just be XI + 1 minus XI, right?
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volunteer
That's just what Delta X just means there's a difference.
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volunteer
We're just comparing um the distance between two x values in this instance.
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volunteer
OK.
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volunteer
Does that make sense so far
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student
yes
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volunteer
I know I'm going, I'm kind of going back and repeating um information you might have already known.
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volunteer
Um
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so, right, so we want to figure out
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student
no no its very helpful
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volunteer
so we've solved for the error value, we find that um Y2 is that the error values you go to Y1 minus
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volunteer
F of X2
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right?
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volunteer
And we can also say
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that Y2
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or sorry, Y of X2.
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is equal to
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M of
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X2 minus X1.
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plus Y1 based based on our uh tangent line
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volunteer
right, which we have up here.
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volunteer
right? All I did was plug in X2 for X.
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volunteer
OK.
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volunteer
But we also know that X2 minus X1 is the same as delta X, right?
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volunteer
So we find that M times delta x
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volunteer
+ Y1
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is equal to YX2
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volunteer
So what they're saying is that Y2 is just equal to Y1
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volunteer
plus the slope, right, the change.
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times the change in X
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which we also know that the slope M
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is just equal to deltay over delta X.
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volunteer
right, which we found up here
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volunteer
Oh, I'm sorry, the Y2 here.
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volunteer
Yeah, I was a little ugly. Let me, um, you're correct, that is supposed to be Y2. The Y2 cannot equal X2
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