### 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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