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1. ### Thinking about taking an astronomy or astrophysics course for fun

Hi all, I've had an itching lately to dive into something new. Currently, I am a professional computer programmer but have always been interested in astronomy. I took an astronomy course (as well as a lab for it) when I was in college and I remember enjoying it all immensely. I want to get...
2. ### Problem dealing with mAH, mA, and volts

So you get 1008 mAH. Each cell's capacity is 250 mAH. But 250 doesn't go into 1008 evenly?

Anyone know?
4. ### Parallel Algorithm for Addition of Two Digit Numbers

I imagine that it is because it requires some overhead work to get two processors working together in the first place.
5. ### Develop the algorithm as a module

I do not understand the pseudocode very well either but I can help... So you got an integer array. And you're looking for a certain number in the array. So this module is suppose to take care of that. How would you traditionally sort through a list of things if you were looking for a certain...
6. ### Problem dealing with mAH, mA, and volts

Suppose the current drain (on average) of a LED is 2mA at 4.5v. Now suppose that 250 mAH 1.5v cells are being used to power this thing. I want to keep this LED powered for 504 hours (3 weeks), how many cells are needed and how should they be arranged? Now, here is my stab at the problem...
7. ### Statistics -> Variance and Linear Combinations

Anyone? Still isn't making sense to me.
8. ### Variance in Statistics

OK, I am having no problem with the concepts here but just with a particular problem. I have analyzed this problem to bits and nothing is working. Here is what we have: The bending capabilities of plastic sheets are investigated by bending sheets at increasingly large angles until a deformity...
9. ### Stuck on how to solve this equation

I graphed the left side of the equation and then graphed the other side (p being X). They do not intersect anywhere. Guess my CDF (Cumulative Distribution Function) is wrong. Ug and to think I got straight A's in all other Math courses so far. This one is just ridiculous. Never take...
10. ### Statistics -> Variance and Linear Combinations

I guess I need to find the expectation value for the second problem first before doing anything, so: integral of x*2x = integral of 2x^2 = 2x^3/3 between 1 and 0 = 2(1)^3/3 = (2/3) = .75 So from there I would just say (.75)^3 as the answer for the expectation value for Y = X^3?
11. ### Stuck on how to solve this equation

Trying to solve for x here... (e^10-11)^-1*(-e^(10-x)-e^10-x) = p So I try: (-e^(10-x)-e^10-x) = (e^10-11)p e^(10-x) = -(e^10-11)p-e^10-x ln(e^(10-x)) = ln(-(e^10-11)p-e^10-x) 10-x = ln(-(e^10-11)p-e^10-x) I get stuck there and don't know what to do. Any help appreciated.
12. ### Statistics -> Variance and Linear Combinations

Having a lot of trouble with a particular problem in the topic of variance. The problem is: "Suppose you are organizing a game where you charge players \$2 to roll two dice and then you pay them the difference in scores. What is the variance in your profit from each game? If you are playing a...
13. ### CS Research Lab Job: Find Summer Work as a Junior

Nope not familiar. Can you tell me what it is?
14. ### Programs Can I be a Math PhD if ?

I agree. No need to try and belittle people. To the original poster, ask a professor at the math department at your school.
15. ### CS Research Lab Job: Find Summer Work as a Junior

Hey guys, I'm in Computer Science and was interested in trying out working at a lab (and actually doing programming work). I was wondering where I could find such a job at these days? I'm pretty sure my university only hires grad students for that kind of work if anything. I will be a junior...
16. ### Implementing Various Calculations ith only + and - in c++

Also, it is apparently obvious that 1 is not prime nor composite so that is never listed. And 2 is obviously prime since there are no numbers between 1 and 2 to check for factors.
17. ### Implementing Various Calculations ith only + and - in c++

Whoops I meant this: for (int i = 1; i <= 100; i++) { for (int j = 2; j < i; j++) { if (i % j == 0) { cout << i << endl; break; } } } Basically once it finds any factor other than 1 and the number itself, then it is not a prime...
18. ### Implementing Various Calculations ith only + and - in c++

This may not be the most efficient method, but try this: for (int i = 1; i <= 100; i++) { for (int j = 2; j < i; j++) { if (Modulus(i, j) == 0) { cout << i << endl; break; } } }
19. ### More CompSci homework help needed

Try: String input = <input from user>... for (int i = 0; i < input.length(); i++) { if ((input.charAt(i) != '0') && (input.charAt(i) != '1')) { // error and quit... } } // success
20. ### Linear Transformation

Oooooh I see now! Thanks so much for your help. That helped tremendously. Now I see where he got the -1 one. It will be on the opposite side of where x1 used to be and x3 will stay in the same spot despite being rotated.
21. ### Linear Transformation

Rotates X2 into ... X3? But why are the coordinates (-1, 0, 0) for that?
22. ### Linear Transformation

OK I still don't really understand what is going on. So you have these standard basis vectors. If we were to do no transformations then the transformation matrix would be: [ 1 0 0 ] [ 0 1 0 ] [ 0 0 1 ] Correct? And based on that, X1 would now have the coordinates (0, 1, 0) making...
23. ### Linear Transformation

OK I already have the answer for this problem but I don't know how my teacher came up with the answer: Linear transformation T in R^3 consists of the rotation around x3 axis at the positive (counter-clockwise) direction at the angle 90 degrees. Such rotation transforms x1-axis into x2-axis...
24. ### Find the following determinants

I know how to find the determinant in general but these two problems here are tough for me: 1. Find the determinant of: 3 -1 0 0 0 -1 3 -1 0 0 0 -1 3 -1 0 0 0 -1 3 -1 0 0 0 -1 3 2. Find the determinant of: 0 2 2 2 2 2 0 2 2 2 2 2 0 2 2 2 2 2 0 2 2 2 2 2 0 Now, I know that I...
25. ### Calculate Density of 3 Stars: White Dwarf, Neutron Star & Black Hole

Alright, I just need to find the density of three stars in g/cm^3. I have been given the following information: Density of a star = Mass / ((4/3)*pi*Radius^3) First star is a white dwarf: Mass = 2 * 10^30 kg Radius = 5000 km Second star is a neutron star: Mass = 2(2 * 10^30) kg...
26. ### Applications of Linear Systems: Electrical Networks

OK here's a revised drawing of the diagram. I labeled the direction of the current this time. Are these directions fine? I know next to nothing about how current, voltage, and resistance work.
27. ### Applications of Linear Systems: Electrical Networks

See that's the thing, he never drew any arrows in the problem. I think he said something like we can make up our own directions but I really couldn't understand him. Would the final answer be the same no matter what the directions were?
28. ### Applications of Linear Systems: Electrical Networks

Hey, How do I find the current through the central resistor (the one that is 1 ohm) in this Wheatstone bridge attached to this post? What approach do I need to take here if I were to solve this using linear systems? Our professor poorly explained how electrical networks work. I can solve the...
29. ### Root 3 + root 2

Wow, I hope I never have to do these kind of problems. What course is this for?
30. ### Solve this linear system using matrices

I tried that with the precise method by leaving alone the irrational numbers (keeping the square roots the way they are). And I end up with this really really long term that just doesn't seem right you know? Thanks for your help though.
31. ### Solve this linear system using matrices

Parth Dave, so what about the calculator part? Would it hold true for the calculator part too? How would I know? Also, if I had problem like: [4*sqrt of 3 5 : 2 ] [5 sqrt of 13 : 1 ] What approach do I need to take here (same subject on solving precisely and solving by...
32. ### Solve this linear system using matrices

One of the questions on a handout was this: Solve the following linear system: A) Precisely B) With a calculator. Since this linear system contains irrational numbers, how would you solve it "precisely"? How would the answer be any different than if a calculator was used? Do I just...
33. ### Solving Gaussian Elimination Algorithm Problems (Matrices)

Thank you gnome. So if any row has this set-up: [ 0 0 0 : Non-Zero Number ] Then it means that it has no solution? Even if it's the second row?
34. ### Solving Gaussian Elimination Algorithm Problems (Matrices)

I tried to solve this Gaussian elimination algorithm problem (matrices) but for some reason when I plug in the x variables it doesn't work. The problem is: Alright so the first thing I did was divide the 1st row by 1/3 (scaling). Then I made the entries below the first pivot equal to 0...
35. ### Solving Gaussian Elimination Algorithm Problem (Matrices)

I tried to solve this Gaussian elimination algorithm problem (matrices) but for some reason when I plug in the x variables it doesn't work. The problem is: Alright so the first thing I did was divide the 1st row by 1/3 (scaling). Then I made the entries below the first pivot equal to 0...