# Learning derivations

1. Feb 8, 2009

### marmot

is it necessary to know where to derive all my formulas, as a general rule? i always try to follow them and understand more or less where they came from, because i hate hand waving. i can derive a good chunk of them, especially the ones of mechanics, but some of the messier ones, like the ones of thermo or em sometimes go over my mind. i can tell you where most of the ones i dont know how to derive come from, but not do the derivation itself. should i try to memorize them?

2. Feb 9, 2009

### mbisCool

I'm sure you can get by in the class without knowing how to derive all of the formulas, but part of truly understanding the material is in the derivations. So I guess it depends on whether you enjoy the subject matter enough.

3. Feb 9, 2009

### marmot

i actually kn ow i dont have to know them to go by the class. but do professors for example, actually remember all those thrifty derivations?

4. Feb 9, 2009

### Brian_C

You don't need to memorize the derivations, but you should understand the steps that are used. That's what physics is all about.

5. Feb 9, 2009

### maze

Here is a good strategy you may want to try:

Whenever you come across something you don't understand from basic principles, give a good shot at deriving it yourself. If it's taking too long and you aren't getting anywhere, make a note of it in the back of your mind and move on. When you learn new things, always be looking to fill in these old gaps.

For example, in a middle school science class I was told that the angle between atoms in a tetrahedron shape is 109.47... degrees. I tried hard but I absolutely could not figure out how to derive it. Then a year or so later when I learned trigonometry, I gave it a second thought and figured out how to solve it. Then a few years later I learned about vectors, gave it a third thought, and figured out how to solve it another way. Then years later in college I started talking about this with a friend, and he showed me yet another more elegant way to derive it.

If you are always filling in the old gaps in your knowledge, you will find that these sorts of convenient occurences happen all the time, and eventually you will have answers to your questions. It may take years, but it will happen.