# Maths for Physics

• Aug 1st 2012, 07:42 AM
Mathsnewbie
Maths for Physics
Hey Guys can you give me some guiding points for a few questions. Trying to refresh myself with doing this kind of work.

1 I) Find Integral of 1/(Cos^2(X)) and 1/(Sin^2(X))

II) Integrate Cos(X)+ [Sin(X)] DX with limits Pie and -Pie. I know the answer is 4 for this but can't get the working right.

III) Similarly Integrate ([u-1]+[u+1]) DU with limits 4 and -3.

With [] symbolosing postive squareroots.

Thanks for any help and apologies for the lay out but any help would be greatly appreciated.
• Aug 1st 2012, 09:55 PM
GJA
Re: Maths for Physics
Hi, Mathsnewbie. I will try to point in the right direction on the first exercise of your post.

You may find that $\frac{1}{\sin(x)}=\csc(x)$ and $\frac{1}{\cos(x)}=\sec(x)$ are relevant. The table involving trig functions and their derivtives at Differentiation of trigonometric functions - Wikipedia, the free encyclopedia may also be of some use. I think this (along with the Fundamental Theorem of Calculus, i.e. taking antiderivatives) is enough to finish off the exercise.

If this is too cryptic let me know and I will try to be more explicit with my hints. Good luck!
• Aug 2nd 2012, 12:37 AM
Mathsnewbie
Re: Maths for Physics
This is great thank you!
• Aug 2nd 2012, 07:32 AM
GJA
Re: Maths for Physics
No problemo. Were you able to get parts II and III?
• Aug 2nd 2012, 07:54 AM
skeeter
Re: Maths for Physics
Quote:

Originally Posted by Mathsnewbie
...
II) Integrate Cos(X)+ [Sin(X)] DX with limits Pie and -Pie ...

fyi, this is pi ...

http://unihedron.com/projects/pi/full_thumbnail.jpg

... and this is pie

http://icons.iconseeker.com/png/full...pkin-pie-2.png
• Aug 2nd 2012, 01:05 PM
Mathsnewbie
Re: Maths for Physics
I managed to get II but struggling with III at the moment.
• Aug 2nd 2012, 01:13 PM
GJA
Re: Maths for Physics
Good job! Keep at it, and if you're totally stumped I can send some thoughts that may put you back on course.
• Aug 3rd 2012, 02:45 AM
Mathsnewbie
Re: Maths for Physics
Would I be right in saying 7 for part III)

My working is

Integral with limits 4,0 (u-1)+(u+1)du + Integral with limits 0,-3 (-u-1)+(-u+1)du

So I get Integral 2uDu + Integral -2uDu with limits 4,0 and 0.-3 respectively

Which equals (U)4,0 + (-U)0,3Which = 4-0 + (0-(-3) = 7