What do you do when you can't follow a derivation in a book?

[BucketOfFish]

Sometimes when studying I'll run into a derivation that seems unclear, unmotivated, or which seems to require outside information. What do you do in those cases? Search online? Bang your head against the equations? Look for another book? I'm specifically asking about learning things on my own, where I can't just ask a professor or a friend who's taking the course.

 

[MidgetDwarf]

Hmm. I re read it over n over again. Make notes in the text as to why things are true. Sometime the book just plain sucks. Rule of thumb. Have at least 2 books of the subject matter. If all fails type it on physicsforum.

 

[MarneMath]

Ask someone to help here or on stack exchange.

 

[PWiz]

I totally understand what you mean because that frequently happens with me. What I try to do to get around this problem is follow some worked examples, put in guess work to understand the steps, and if all fails, find my own derivation. Yes, I know it sounds crazy, but finding your own derivation(and reaching the correct final equation of course! ) is probably the best way to understand something for good. You can always post your derivation here on PF and check if you did it right. Hope that helps :)

 

[thegreenlaser]

This happens to me fairly often. Usually I would (roughly in order):
1. Bang my head against it
2. Try to find a better explanation online
3. Try to find a better explanation in a book at my school's library
4. Ask online or ask the professor

Don't spend too much time banging your head against it. I find that seeing multiple explanations from multiple people can really help to clear things up.

Also, sometimes if you leave it, move on, and then come back to it later, you'll find that things make more sense. Seeing how a result is used and applied can help motivate the derivation.

Finally, pick your battles. If you can understand and apply the final result, it may not be worth your time to fully understand the derivation (unless it's a really key derivation or the derivation is the result).