# Recent content by der.physika

1. ### Bifocul Optics Problem Help Please

Homework Statement A woman is wearing bifocals that have one-half of the lens with a power of -1.2 D and the other with a power of 1.8 D. A lens provides her with a far point set at infinity and other will give her a near point of 25 cm. Where are her near point and far point WITHOUT her...
2. ### T-shirt problem!

okay, so I am making an astrophysics/physics shirt and I want it to be really funny. anyone have any ideas?
3. ### Taking Electrodynamics this semester

I am taking Electrodynamics this semester and we are doing the course with the aid of "david griffith's Intro to electrodynamics" there has been alot of word that the course is extremely difficult... can anyone tell me ways to prepare for it?

wow thank you so much for telling me this in detail. I appreciate it very much... did you go to graduate school as a physics student? and are telling me from first hand experience?

Hello, I am a undergraduate Physics student and I heard that if you pursue a graduate degree in Physics for grad school (not undergraduate) the department pays your tuition for you? Is this true? I have 5 friends that they have finished undergraduate physics (payed their OWN tuition) but...
6. ### The Geometry of Maps (Help)

Okay... I think I found the solution by using parametric equations (t,0); (1,t); (t,1), (0,t) and plugging them in yields (0,0), (0,0), (t,t), (0,t) which makes it not 1 to 1. So... it gives me the triangle with those vertices. is this correct?
7. ### The Geometry of Maps (Help)

Homework Statement Let D* = [0,1] x [0,1] and define T on D* by T(x*,y*) = (x*y*, x*). Determine the image set D. Is T one-to-one? Homework Equations The Attempt at a Solution Okay... So I know it is not one to one, if you take out the point (x=0) then it is one-to-one, so you...
8. ### Vector Calculus Question (I don't understand)

Okay... so I took your advice. so I thought about what you said so T(u,v) maps u => -u^2 + 4u and v to v so for u [0,1] is the interval... so that means [0, -1+4] = [0,3] for v [0,1] goes to [0,1] [0,3] x [0,1] so that means... it maps the square into a rectangle. But...
9. ### Vector Calculus Question (I don't understand)

Homework Statement Let D* = [0,1]x[0,1] and define T on D* by T(u,v)=(-u^2+4u, v). Find the image D. Is T one-to one Homework Equations The Attempt at a Solution I have no idea... I don't know how to do it. The solution is [0,3] x [0,1]... yes it is one to one. am I supposed...
10. ### Absolute Max/Min

Can anyone tell me the general procedure in doing the following procedure? f(x,y)=xy^2 with domain x^2+y^2\leq4 Find it's absolute max & absolute min. Okay, here is my thought procedure, tell me what I can fix. So I would basically say, find the partial derivatives with respect to x and y...
11. ### Syl & Der

What are the equations that describe simultaneity, and hey don't be afraid to throw some math out there. All though I might not be able to grasp things like the Ricci Curvature just yet, I could still derive the equations for Time Dilation & the Lorentz Contraction, so please show me the math, I...
12. ### Differential Equations WTF?

Okay, so I was sitting in my room wondering about the differential operator D. Like for example, solving the equation y\prime\prime+5y\prime+4y=0 introduce D=\frac{d}{dx} (D^2+5D+4)y=0 so you can solve it by doing D=-4, D=-1 e^-^4^x+e^-^x is the solution But how the hell do you solve...
13. ### Syl & Der

Me and my friend Syl consistently talk about Special Relativity and it's effects in nature when electrodynamic bodies move at relativistic speeds. I wanna make a discussion. What is Special Relativity? How does it work? How much do we understand?
14. ### Double Integral

How do you put in limits on the integral? I don't know how to put the code into LaTex
15. ### Double Integral

\int\int(yx^2dydx)-2\int\int(xy^2dydx) \int[\frac{1}{2}y^2x^2]=\int(-2x^2dx)=[\frac{-2}{3}x^3]=\frac{-54}{3} -2\int\int(xy^2dydx)=-2\int[\frac{1}{3}y^3x]=-2(-12)=24=\frac{72}{3} =\frac{72}{3}+\frac{-54}{3}=\frac{18}{3}=6 is this okay?