Recent content by de1337ed

I'm a little confused about some of the matrix terminology. I have the following subspace: span{v1, v2, v3} where v1, v2, v3 are column vectors defined as: v1 = [1 2 3] v2 = [4 5 6] v3 = [5 7 9] (pretend they are column vectors) How am I supposed to find the dimension of the span? My...

Homework Statement Equations: \frac{dv_{1}}{dt} = -v_{1} - \frac{2v_{2}}{3} + 1 + \frac{t}{3} \frac{dv_{2}}{dt} = -2v_{2} - 1 - 2t Initial Conditions: v_{1}(0) = 6 v_{2}(0) = -6 2. The attempt at a solution Defined the following: v(t) = [ v_{1}(t) v_{2}(t) ] \frac{dv(t)}{dt} = [...

Let A and B be n×n matrices, and let v be a column vector of length n. Which of the following two expressions is faster to compute? 1. ( A⋅ B )⋅ v or 2. A⋅ (B⋅ v) As a function of n, give the number of multiplications and additions required for each part. My attempt: So, I said that (2)...

Problem: An Si resistor is at 300Kelvin, and is 100μm long, 1μm thick, 5μm wide. The conductivity is 7.128 Ωcm. The resistance is 28058Ω. A voltage of 5v is applied. What is the drift velocity of the electrons, given that n = 1.01x103? Other constants: μn = 1350 cm2/Vsec μp = 450 cm2/Vsec...

Homework Statement Point is chosen at random (uniform PDF) within semi-circle: {(x,y)|x2+y2≤r2, y≥0} Basically, I'm supposed to find E[X] for this problem 2. The attempt at a solution I know how to do it, in a very long-winded fashion (find fY(y), and E[X|Y=y] etc). But my teacher says that...

Hmm, i see, okay. I think I'm doing something wrong, I'm getting the fact that E[x] = 1.726... E[x2] = ∫x2*2x-2dx from 1.5 to 2. This gives me 1 As a result, I get the variance to be 1-(1.726)2 = -1.979. Which doesn't make sense because isn't the variance supposed to be ≥0? EDIIITTT...

So basically, I got that P(A) = 1/3. And fX|A(x|a) = 6x^-2, 0<x<0.5. (This range confuses me, I'm not sure about this) and 0 otherwise Then E[x] = ∫x*6x-2dx. From 1.5 to 2. And then Variance would be E[x2] - (E[x])2 Am I right?

Oh shoot, copied the problem down wrong, its actually cx^-2

Ya I found the value of c to be 2. And ya, I know that is the formula, but I didn't know how to calculate P(A)... Is it simply the ∫fX(x)dx from 1.5 to 2?

The random variable X has the PDF fX(x) = cx^-2 if 1 < x < 2; 0 otherwise: (a) Determine the value c (b) Let A be the event fX > 1.5. Calculate the conditional expectation and the conditional variance of X given A. I'm not understanding the concept of conditional pdf's. Can someone show me the...