# Search results

1. ### Finite Fourier Transform on a 3d wave

Finite Fourier Transform on a 2d wave How does the finite fourier transform work exactly? The transform of f(x) is \widetilde{f}(\lambda_{n}) =\int^{L}_{0} f(x) X_{n} dx If I had a 3d wave equation pde and I applied Finite fourier transform on the pde for z(x,y,t)=X(x)Y(y)T(t)...
2. ### Proof using f(x1,y1)-f(x0,y0)=fx(x*,y*)(x1-x0)+fy(x*,y*)(y1-y0)

1. Homework Statement [/prove f(x1,y1)-f(x0,y0)=fx(x*,y*)(x1-x0)+fy(x*,y*)(y1-y0) prove there exists a point (x*,y*) if fx and fy are all continuous on a circular region and contain A(x0,y0) and B(x1,y1) 2. Homework Equations [b]3. The Attempt at a Solution I'm thinking mean value...
3. ### How do you tell what a vector space will look like from it's spanning set.

I'm having a hard time visualising them. How do you plot vector fields How do you plot spanning sets? How do you tell if something spans a plane, 3d, a line or more dimensions.
4. ### Basic basic javascript form validation. literally need an help

Javascript is in an external file liked by this: <script type="text/javascript" src="myscript.js"></script> in the head tag i have <form name="myform" action="" method="POST" onSumbit="return validateForms()"> and some form stuff and then: <input type="submit" value="Submit"...
5. ### Implicit partial differential for unknown function F(x,y,z)=0

1. Homework Statement F(x,y,z)=0 x=a(y,z) y=b(x,z) z=c(x,y) what does \frac{\partial c}{\partial x} \frac{\partial b}{\partial z} \frac{\partial a}{\partial y} equal. 2. Homework Equations maybe you could tell me? 3. The Attempt at a Solution i've spent hours and hours...
6. ### What does 2nd ord pde tell you? like fxx(x,y)

pure and mixed, what do they tell you about a function?
7. ### Wht does this sign mean?

(\frac{\partial z}{\partial x})y the small y, what does it mean. the context this is used in is F(x,y,z) where each variable is a function of the other 2 variables.
8. ### Volume under curve z=1-x^2-2y^2

1. Homework Statement z=1-x^2-2y^2 find volume under curve bounded by the xy plane. is the answer sheet wrong? (see below) why am i struggling so much with this??!?!?! how do i do it? 2. Homework Equations according to other answer sheet, it is pi/sqrt 2 3. The Attempt at a...
9. ### Vector space prove 0u=0

1. Homework Statement prove 0u=0 where u is in the vector space. 2. Homework Equations the 10 various axioms for addition and scalar multiplication. 3. The Attempt at a Solution pretty much just (u+-u)u=0 or (1-1)u=0 1u+-1u=0 and then i get stuck. i can prove that...
10. ### Show its not a group for # where a#b=a+b-ab in the set of all real numbers

1. Homework Statement In set theory, i have a two part question, the first is showing that the system S={set of all real numbers( \Re )}, #} where a#b=a+b-ab we have to show that it's not a group. and then find what c is so that the system = { \Re \cap\overline{c}, # } is a group. 2. Homework...
11. ### 3-10 points why you believe in the theory of evolution and big bang

Can you give me 3-10 points why you believe in the theory of evolution and/or the big bang? this is independant of any other theories. I'd like it numbered. and just brief points, like a topic and brief explanation of why this makes you believe evolution and/or the big bang to be true. I'll...
12. ### What is 3 digit arithmetic?

what is 3(or i, where i=1,2,3,4......∞) digit arithmetic? is it just working with 3 decimals or 3 significant figures? or is it base 3 arithmetic?
13. ### RFID attendance marking, what infrastructure?

RFID attendance marking, what infrastructure?? im trying to plan for an RFID system. 1)what resources and material and general infrastructure do i need? 2) i think i want it to connect it up to my Uni's intranet maybe wireless, so i'd only need to wire the power source? this good? 3)...
14. ### MATLAB Basic matlab q on writing error messages

How do you write error messages for when a function has been given an input that is illogical for what the function does. in matlab function b = bla(a) for example if a < 0 i want it to display a message
15. ### Conditional Probability

1. Homework Statement romeo proposed to juliet. now hes waiting for her response. R = 'event that she replies' W='event that she wants to get married' Mon = 'event on monday' Tue = 'event on Tuesday' P(R\wedgeMon | W) = 0.2 P(R\wedgeTue | W) = 0.25 P(R\wedgeMon| \bar{W}) = 0.05...
16. ### MATLAB Matlab and floating point, function for min n max?

so i found this program matlab on the computers at uni. ive been messing around with it. right now im learning a bit about floating point systems and stuff and i thought it would be cool to write up a function that finds the smallest and largest numbers but turns out its harder than i first...
17. ### Questions and answers for a test covering a variety of things?

im trying to study but i have um misplaced my textbook. (it ran away from me, after i neglected it whilst doing other assesments) so i would greatly appreciate just a couple questions with answers, (feel free to give me more though ;) ) on any of these things (in order of priority) -...
18. ### Check my working for finding if vectors are parallel ?

1. Homework Statement there is a line through A : (1;-2; 1) and B : (0; 2; 3) and the line through C : (4; 1;-2) and D : (2; 2; 2) are they parallel? 3. The Attempt at a Solution i said no they weren't. i had the lines as being: (-t+1)i+(4t+2)j+(2t+1)k and (-2t+4)i+(t+1)j+(4t-2)k...
19. ### When integrating by trig substitution why do you use what you use?

when integrating by trig substitution why do you use what you use?? for example int. (1+x^2)^0.5 dx why do you use x= tan u i mean obviously because it works, but if you didn't know it works how would you figure it out? i would think that you should use x=sinh u but ive been trying...
20. ### Some questions for non/homogeneous equations

what do you do when m=0, do you just have 1 term + a constant? what do you do when there is only 1 value for m. do you have Ae^mt + Ate^mt or what? im a little confused. EDIT -for differential equations i mean, when youre trying to solve for y and the equation has differentials of y in...
21. ### Is there any point in buying cloud services locally or internationally or what?

pros and cons if any?
22. ### Is it mathematically sound to do this

apply integration by parts twice and swapping the u and v's and then rearranging the equation to say that it is equal to bla/2 like for example i said u is x^n or something and v' is sin x or something. later on when im faced with another integral, i apply the int by parts but this time...
23. ### Laplace of non-homogeneous

1. Homework Statement do a laplace transform on a given non homogeneous equation. to eventually find out y 2. Homework Equations i dont think the equation is needed. however this non homogeneous equation is equal to Ae^kt 3. The Attempt at a Solution well. i applied the laplace...
24. ### On a scale of 1-100 how bad is my graphics card?

1 being the worst you can buy right now, 100 the best you can buy right now i got a mobile intel R 4 series express chipset family with a booster: nvidia geforce G210M cuda 512Mb i think thats right. >.> could be wrong though :s the dxdiag window thing just says the mobile intel r 4 stuff but...
25. ### Can someone explain Laplace transformations

Can someone explain Laplace transformations!!!!!!!!! i dont understand ittttt.  sorry. i hadnt even heard of laplace transformations until i found it in my assignment. basically i want to know how to use them so, some simple, well explained examples perhaps?
26. ### General solution of integration by parts of int(x^n*e^x)

1. Homework Statement i have to create a general formula for integral of (x^n * e^x) dx using whatever method i deem appropriate. (the only way i could think of is by parts) 2. Homework Equations int(x^n * e^x)dx int(uv')dx=uv-int(vu')dx 3. The Attempt at a Solution i used...
27. ### When does a limit not exist.

I cant remember exactly. I'm thinking its when its not continuous or differentiable. but is there more exact definitions/am i wrong/anything really.
28. ### I^2 = -1 or +1

i was taught that i2 = -1 because ((-1)1/2)2=(-1)2/2=(-1)1=-1 but isnt it mathematically correct to say \sqrt{-1} * \sqrt{-1} = \sqrt{-1*-1} = \sqrt{1} = 1 what the heck!! Is there some bleedingly obvious thing im missing.
29. ### Reverse product rule?

1. Homework Statement i'm sorry i know i've been bombarding physics forums with questions but i need help :p using reverse product rule \int uv' = uv - \int vu' and say i have a*b i noticed my teaher said that a=u and b=v not v' and he simly made that into a v' by deriving. is there a...
30. ### Exponential Integral

1. Homework Statement i have to integrate e^(-y) / y and i found out that you have to use this exponential integral and someone else said it doesnt have an integral. either way im thoroughly confused 3. The Attempt at a Solution i have no clue what so ever. The original question had it...