Tilted Forum Project Discussion Community - View Single Post - I Can't Understand dy/dx when you throw in "u"

Slavakion · 03-09-2005, 07:18 PM

Let's take a function. y=3x
The derivative of this can be written as dy/dx = 3. I assume by "u" you mean du/dx, right? Well, the common form of the derivative expression thing is dy/dx because you're usually taking the derivative of y with respect to x. In other words, you're solving for y, and finding the derivative of it.

You could have any other variables in there, like ds/dt or dx/dp. The thing that signifies a derivative is the "d" that precedes the other variable. So we have y, and we have dy. The general form for a derivative (which is what's used in theorems) is du or du/dx. Just sub in y or whatever.

If you're wondering why it's always dy over dx, it's because you're essentially dividing. y=3x would be differentiated into dy=3dx, which would be simplified to dy/dx=3.

There ya go, an unfocused crash course in differential variables. If your teacher really does suck, I suggest going to Borders and picking up an AP study guide for calculus. They'll come with AB and BC in it, so you'll be set for about a semester and a half of calculus. Or you'll be set with your AP class if you're still in high school. Good luck.

03-09-2005, 07:18 PM	#3 (permalink)
Slavakion Mjollnir Incarnate Location: Lost in thought	Let's take a function. y=3x The derivative of this can be written as dy/dx = 3. I assume by "u" you mean du/dx, right? Well, the common form of the derivative expression thing is dy/dx because you're usually taking the derivative of y with respect to x. In other words, you're solving for y, and finding the derivative of it. You could have any other variables in there, like ds/dt or dx/dp. The thing that signifies a derivative is the "d" that precedes the other variable. So we have y, and we have dy. The general form for a derivative (which is what's used in theorems) is du or du/dx. Just sub in y or whatever. If you're wondering why it's always dy over dx, it's because you're essentially dividing. y=3x would be differentiated into dy=3dx, which would be simplified to dy/dx=3. There ya go, an unfocused crash course in differential variables. If your teacher really does suck, I suggest going to Borders and picking up an AP study guide for calculus. They'll come with AB and BC in it, so you'll be set for about a semester and a half of calculus. Or you'll be set with your AP class if you're still in high school. Good luck.