Related Rates Test: North-South-East-West Rate of Change on TI-89
Raw Transcript
hello everyone Tom from every step calculus dot com
uh, gonna do a related rates problem
with north and south and east and west type of problems that
occur on tests, and planes going north and going east and
what’s their rate of change etcetera and
we’re gonna do a number 6
in this example put index eight in here to get the calculus one
menu and we’re gonna scroll up to get to the bottom of the menu and get two related
rates
press Enter
and we’re gonna do
north south east or west number 4 here press 4 or you can scroll to it like with
the cursor here
or you can just press the number before
you write this on your paper x
squared plus y squared equals z squared we’re going to do the derivatives of each one
d/dt of x squared plus y squared on this side of the problem
and z on the other side here’s what you get
you get 2x..derivative of x squared is 2x
etcetera derivative
of y squared is 2y respect of t which is time
and same thing with 2z the 2’s go out
you can divide through by 2 and so you get this right here
write all this on your paper just exactly as you see it nothing left out
the only things that
dx/dt is given that means that the x axis
horizontal is what their after
let’s see, a man begins walking
due North so due North is the y so
it wouldn’t be that one, so the woman is walking east
which is on the x axis
so were gonna do alpha always press alpha
before you enter anything in these entry lines here alpha 4
and then the Y
the man is going north so he is going alpha 3
and after time of one hour what’s happening alpha
1, show you what you’ve entered so you can change in case you made a mistake, it’s
okay
write this on your paper x is dx/dt over t is at 4 over 1
your entering all the variables here
x equals 4 y equals three
and then we can do
the pathagoram Theorem all this is easy if you know it but I mean on a test
even if you do know it is nice to do a problem quickly and be done with it
and get 100% on it and move on to something else so Z equals five
so that’s the answer 5 miles per hour
make sure you write all this on your paper
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