# Recent content by theloathedone

1. ### Sum of Dice Rolls

Haha me too. Thanks Ray for the help, I'll try to understand it :)
2. ### Sum of Dice Rolls

Ok, what I did was to draw out two tables. The first one is here: 1st Dice 1 2 3 4 5 2nd 1 2 3 4 5 6 2 3 4 5 6 7 3 4 5 6 7 8 4 5 6 7 8 9 5 6 7 8 9 10 If Y = X1 + X2 So...
3. ### Sum of Dice Rolls

Homework Statement There is a 5-sided fair dice with faces showing 1, 2, 3, 4, 5 dots. The dice is rolled four times. Find the probability of getting a total score between 10 and 15 (inclusive). Homework Equations If X is the score from one roll, then it follows a discrete uniform...
4. ### How much sleep do you need in school?

Haha sadly this is so true
5. ### How much sleep do you need in school?

Ok to clarify I meant, how much sleep did you get during your schooling years... :)
6. ### How much sleep do you need in school?

Hi all, just out of curiosity, how much sleep did you get in school (high school, college etc.)? I'm a high school student from Singapore, and I average under 6 hours of sleep per day. But in my school, I get more sleep than probably about 80% of the student population. I know some who get...
7. ### Square a random variable

yup. it's 0 for x < 0 and 1 for x > 25. Thanks for the help :)
8. ### Square a random variable

Ah I see where I went wrong. But it should be 0.2\sqrt{x} and not \sqrt{0.2x} right? Thanks for the speedy responses!
9. ### Square a random variable

Homework Statement Let the random variable X represent the length of the side of a square. It has a uniform distribution over the interval (0, 5). What is the cumulative distribution function for the area of the square, Y? Homework Equations F(x) = 0.2x (the cdf of the side). The...
10. ### 3V Battery Indicator Circuit?

Yup I'm looking at that schematic, which is for a 6V battery. Thanks Sciurus, I didn't think of that even though I have a few diodes lying around. So I guess instead of a Zener diode in reverse bias, I could just use (say 3) normal diodes in forward bias to get a 2.1V voltage drop, so the...
11. ### 3V Battery Indicator Circuit?

Hi, I'm not sure if this is the right place to post this, but here goes. I'm trying to build a battery indicator circuit for 2 AA batteries (3V). So far what I've read online is that I'd need to use a Zener diode to get a fixed voltage drop, then connect it to a transistor, like the...
12. ### Kinematics in Polar Coordinates

Thanks ehild for pointing out my mistake :) I seem to be making alot of careless mistakes on this problem. So after correcting that cos in the denominator, I managed to get answers that sound reasonable, like 30 seconds. I think it should be right now. Thanks for all the help! Really...
13. ### Kinematics in Polar Coordinates

Ok I tried using Wolfram Alpha to do the numerical integration. \frac{d\theta}{dt}=\frac{u \cos{\theta}}{r(\theta)} = \frac{u}{K}|\sec{\theta}+tan{\theta}|^{-\frac{v}{u}} So can I just separate the variables and get dθ|sec(θ)+tan(θ)^(v/u) = u/K dt? When I used Wolfram Alpha to perform the...
14. ### Kinematics in Polar Coordinates

Yeah it is ugly, but I'm allowed to use numerical integration. Oh yeah I made a mistake in the signs, all of them should have been negative in the original expression for the velocity. So after integrating, I got r(θ) = K cos(θ)|sec(θ)+tan(θ)|^(v/u) The particle starts at (d, 0), and I...
15. ### Kinematics in Polar Coordinates

Yup u and v are constant. Is this set of DE solvable? Edit: After looking at another problem from this forum, I think it would be possible to express it in terms of dr/dθ. \frac{dr}{d\theta} = \frac{dr}{dt} \frac{1}{\frac{d\theta}{dt}} = ur \tan{\theta} - \frac{vr}{u\cos{\theta}} And this...