A maths problem

[Napalmbrain]

Maths is useful, at least in some fields, e.g. engineering. Since I do physics I have to use calculus all the time, sometimes quite complicated equations. I hate those trigonometric ones, I can never remember the trigonometric identities you have to use.

 

[zeon9881]

i ant wait till i go to high school and fininsh and go to uni and finish and then finally med school

 

[Cadbury]

e^xy = 5

xy = ln5

y + x.dy/dx = 0

dy/dx = -y/x

There is your answer.

 

[Oceanic]

you are trying to differentiate something with two variables, x and y. Therefore, you need to differentiate with respect to either x or y, not both (this is partial derivatives)
So if you differentiate with respect to x, then your answer is ye^xy and if with respect to y, your answer will b e xe^xy, using the chain rule.

 

[jowii]

I'm in med school right now, and calc has definitely come in handy (which is prolly why its required).

A lot of the pharmacokinetics stuff (drug doses, where it goes, and how long it takes to leave the body) uses a lot of calc. For instance any given drug, with a few exceptions, is eliminated from the body as an exponential decay function. The other really helpful part is just the way you learn to think about rates in calc. Even if you don't use the chain rule, etc, in everyday life, it helps you think about some problems in cool new ways.

 

[Cadbury]

you are trying to differentiate something with two variables, x and y. Therefore, you need to differentiate with respect to either x or y, not both (this is partial derivatives)
So if you differentiate with respect to x, then your answer is ye^xy and if with respect to y, your answer will b e xe^xy, using the chain rule.

I'm not sure if you are disagreeing with me, but what I posted earlier is the right answer.

 

[Oceanic]

I'm not sure if you are disagreeing with me, but what I posted earlier is the right answer.

I didn't read that post on my first look through, you never said in your original post that the equation equaled 5. My answer was correct based on what you told us in your first post, that's why my answer is different from yours. You cant forget to tell us information:hand:

 

[Cadbury]

When you differentiate the 5 disappears and becomes irrelevant, so it doesn't matter whether the 5 was there or not.

 

[Napalmbrain]

Cadbury, you're quite correct but you forgot to mention you specifically wanted dy/dx, not differentiate e^xy.

 

[kissoff182]

=)
Oops.