Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#26 Help Me ! » Differentiation. » 2005-12-14 04:31:21

Tredici
Replies: 11

I've had a good look at all the existing topics based around this rather annoying subject, but nothing seems to satisfyingly relate to what I'm questioning. I don't quite understand how special functions react to differentiation, well I suppose I do, if basic differentiation. I'm just really having problems with questions involving the differentiation of multiple functions that are multiplied or squared.

There's a heck of a lot of questions I'm having problems with, and I'd much rather learn how to solve them as oppose to watching someone else work through it for me. So, I was thinking, would it be possible if someone could fill out a list of how the functions are differentiated, maybe if I were to provide a structure? At least, I know this:

f(x)          f'(x)   

sin(x)          cos(x)
cos(x)      -sin(x)
tan(x)         sec²(x)
sec(x)         sec(x)tan(x)
cosec(x)   -cosec(x)cot(x)
cot(x)          -cosec²(x)
ln(x)           1/x
e^x          e^x



I know, it's not much at all, but I'm just quite unsure of the following:




f(x)              f'(x)   

sin(ax)         
cos(ax)       
tan(ax)         
sec(ax)         
cosec(ax)     
cot(ax)         
ln(ax)             
e^(ax)         



f(x)            f'(x)   

sin²(x)       
cos²(x)       
tan²(x)       
sec²(x)         
cosec²(x)   
cot²(x)             
ln²(x)           





f(x)               f'(x)   

a x sin(x)         
a x cos(x)         
a x tan(x)         
a x sec(x)         
a x cosec(x)   
a x cot(x)         
a x ln(x)           
a x e^(x)       


and finally, just as an example:



f(x)                          f'(x)   

a x sin(bx + c)     
a x cos(bx + c)         
a x tan(bx + c)         
a x sec(bx + c)         
a x cosec(bx + c)     
a x cot(bx + c)         
a x ln(bx + c)               
a x e^(bx + c)         



I'd be eternally greatful if someone could show me how the above are differentiated. I understand it's an extensive list, maybe excessive, so it's perfectly understandable if you don't have the time for me, but I'm just eager to get to grips with this, as to cease resorting to this comunity with similar questions. Thanks so much for your time, I really do appreciate it. David.

#27 Re: Help Me ! » Double/Half Angle Difficulty. » 2005-12-12 08:47:13

In the time it took you to do that for me, I had a quick browse around the forum, I don't really know what to say. All I can say is you're all incredibly good at maths, and I really hope you don't mind a not so strong mathematician like myself crashing your parade.

'Mathsyperson', thank you very much. Probably the most annoying thing about maths is once you know the answer getting to it is is a heck of a lot easier. Thanks again my friend!

EDIT: Mathsyperson, are you interested in taking on an apprentice? smile.

#28 Help Me ! » Double/Half Angle Difficulty. » 2005-12-12 08:26:13

Tredici
Replies: 7

Hey there, I'm not sure where the majority of this community reside, but I'm David and I live in England. I study Maths at A2 Level, (C3). I'm not sure if that's what it's called overseas but I hope it's the same or there's an equivalent.

Anyway, I'm having problems with double and half angle formula application and useage. I've been given a question, and I'd be so undoubtedly greatful if one of you mighty maths minds could work it through for me. Here it is:

Using the identity for cos (A+B), prove that cos θ = 1 - 2 sin² (½θ).

Probably looking at this, you're thinking I'm a complete amateur, but I don't have a clue; I'm stumped. Please help!

Cheers, David.

Board footer

Powered by FluxBB