Points Definition and 1000 Threads

  1. PainterGuy

    B Are there any points other than the origin where cosines are totally in phase?

    Hi, This question just came to my mind and I thought I should confirm it. Are the cosine functions with the same amplitude but different frequencies are totally in phase at any other point other than the origin? The frequency, f, could be anywhere between 0 < f < ∞. I'm sorry if the answer is...
  2. D

    I The fastest route between two points

    Hello, Consider the next scenario: I wish to travel from point a to point b as fast as possible. Between the points there is a border. In the region from a to the border, I can move only with velocity v1, and after the border, I am allowed to move only with velocity v2. All the additional...
  3. A

    MHB Check if two points are symmetrics/asymmetric

    I'm working on an Android app which let's a group of child to draw whatever they want in a specific area. I need to check if the lines and figure that they draw are symmetric. The problem is that since the app is designed to let them draw freehand, I don't know how to compare the lines by...
  4. Andsello

    B Check if two points are symmetrics/asymmetric

    I'm working on an Android app which let's a group of child to draw whatever they want in a specific area. I need to check if the lines and figure that they draw are symmetric. The problem is that since the app is designed to let them draw freehand, I don't know how to compare the lines by...
  5. M

    I What if the Jacobian doesn't exist at finite points in domain of integral?

    Consider a one to one transformation of a ##3##-##D## volume from variable ##(x,y,z)## to ##(t,u,v)##: ##\iiint_V dx\ dy\ dz=\int_{v_1}^{v_2}\int_{u_1}^{u_2}\int_{t_1}^{t_2} \dfrac{\partial(x,y,z)}{\partial(t,u,v)} dt\ du\ dv## ##(1)## Now for a particular three dimensional volume, is it...
  6. karush

    MHB Finding the Equation of a Circle Passing Through Three Given Points

    find an equation of the circle passing through the given points 85 Given $(-1,3),\quad (6,2),\quad (-2,-4)$ since the radius is the same for all points set all cirlce eq equal to each other $(x_1-h)^2+(y_1-k)^2=(x_2-h)^2+(y_2-k)^2=(x_3-h)^2+(y_3-k)^2$ plug in values...
  7. B

    MHB Finding Cluster Points/Accumulation Points

    Find the set of cluster points for the set A := {(−1)n/n : n ∈ N}. Justify your answer with proof. I believe 0 is a cluster point but I can't figure out how to prove this, or how to prove any other point is not. Any quick help would be appreciated. Thanks.
  8. SamRoss

    Trying to use polar coordinates to find the distance between two points

    ##{dx}^2+{dy}^2=3^2+3^2=18## ##{dr}^2+r^2{d\theta}^2=0^2+3^2*(\theta/2)^2\neq18## I have a feeling that what I'm doing wrong is just plugging numbers into the polar coordinate formula instead of treating it as a curve. For example, I naively plugged in 3 for r even though I know the radius...
  9. A

    I Function value at different points

    If for a field say ##f=xyz## ,it's value is defined at 10 points in the 3-D Cartesian co-ordinate system...now using these 10 values of f and the corresponding coordinates is it possible to find the value of f at any ##(x,y,z)## of choice??
  10. forever_physicist

    A Inequivalent K and K' points in graphene

    Good evening to everybody! I have a question concerning monolayer graphene. In all the papers I read it is well specified that K and K' in graphene are not equivalent points, but I didn't find anywhere where is the difference between them. Can anybody tell me where this difference is coming...
  11. T

    Crystal with two different melting points

    It turns out that the solid form is the same for the two situations but the liquid is two different isomers depending on external conditions during melting. https://physicstoday.scitation.org/do/10.1063/PT.6.1.20190606a/full/
  12. J

    I Can the area be understood as the "number of points"?

    In Euclidean geometry (and even in measure theory, see for example Stein and Shakarchi's Real Analysis), distance in the real numbers is defined as the difference of the real numbers, and area of a square is understood as the product of the distances defining the given square (and the same for...
  13. C

    Gradient of a function at many points, referencing a struct

    I want to compute the gradient of some smooth function at many points by taking the value of the function at point x(i) subtracted from the value of the function at point x(i+1) and then divide the result by ( x(i+1)-x(i) ). My function has a struct as an argument and within that struct I have...
  14. Calculuser

    I Family of Circles at Two Points

    As I was flipping through pages of my analytic geometry book from high school, in circle section I stumbled across the formula of "family of circles intersecting at two points" with two circles (##x^2 + y^2 + D_1 x + E_1 y + F_1 = 0## , ##x^2 + y^2 + D_2 x + E_2 y + F_2 = 0##) known to intersect...
  15. maistral

    I Fitting points z = f(x,y) to a quadratic surface

    Hi! I am aware that standard fitting numerical methods like Levenberg-Marquardt, Gauss-Newton, among others, are able to fit a dataset z = f(x,y) to a quadratic surface of the form z = Ax2 + Bxy + Cy2 + Dx + Ey + F, where A to F are the coefficients. Is there a simpler method that exists? I'm...
  16. Robin04

    Distribution of distances from the origin of randomly generated points

    I'm not really sure how to do this. Maybe somehow I should transform the density function. Can you give me a hint?
  17. karush

    MHB 141.30 how many points of inflection will the graph of the function have

    If the derivative of a function f is given by $$f'(x)=\frac{1}{5}(x^2-4)^5-x^2$$ how many points of inflection will the graph of the function have?solution find $f"(x)$ $$f''(x)=2x((x^2-4)^4-1)$$ at $f''(x)=0$ we have factored $$2 x (x^2 - 5) (x^2 - 3) (x^4 - 8 x^2 + 17) = 0$$ then...
  18. K

    MHB Finding Horizontal/Vertical Distance Between Two Points in Scratch 3.0

    I am making a Scratch 3.0 game. The shooter sprite is holding a gun slightly off-centre (see images), and I need the bullet to go to the end of the barrel of the gun before traveling forward (as so it would appear the bullet it leaving the gun). The issue is, to do this, I need to find the X and...
  19. S

    B Why do pictures of stars have 4 cardinal points?

    I've noticed that a lot of these pictures are like this. Is it something to do with the error in the machining of the lenses?
  20. M

    Distance between fixed points of contracting maps

    Homework Statement Let ##V## be a Banach space. Let ##f:V\to V## and ##g:V\to V## be two ##q##-contracting maps, ##q\in(0,1)##. Assume they are uniformly close to each other. Show the distance between fixed points of ##f,g## is at most ##\epsilon/(1-q)##. Homework Equations Definitions...
  21. Kyueong-Hwang

    What are the lattice points for this?

    In picture, there is crystal structure with two atoms. Question is, what is the lattice points? Find a set of lattice points. I think green and pink points are both lattice points. Am i right? This is our full hw.
  22. Mr Davis 97

    Minimizing the distance between two points and a line

    Homework Statement Let ##A## and ##B## be two given points, ##l## a given line. Find the point ##P## on ##l## such that ##|AP-PB|## is a maximum. Homework EquationsThe Attempt at a Solution Suppose that the line ##l## and the line that goes through ##A## and ##B## (call it ##\ell_{AB}##) are...
  23. R

    Extrapolating data points using models

    Homework Statement I have made a number of measurements of current against optical power for a given laser. As shown below, my measurements only go up to 8 amps. I am trying to use the data to predict the output power at 9 amps. In the ideal case, the behaviour is expected to be linear, but...
  24. M

    Same pressure points , 2 fluids u shaped tube

    Homework Statement see pic uploadedHomework Equations Pascal principal p = ρgh The Attempt at a Solution Pressure at C and D is the same . Pressure at A and B is the same ? I believe it is
  25. D

    Radius of curvature of the trajectory of points A and B

    Homework Statement A cylinder rolls without slippage on a horizontal plane. The radius of the cylinder is equal to r. Find the radious of curvature of the trajectory of points A and B. Homework Equations Ciruclar motion equations. ##R=\frac{1}{C}## The Attempt at a Solution First I drew the...
  26. CCMarie

    B Finite distance between two points

    If X is a metric space, what is the simplest sufficient condition for d(x,y)<∞, ∀ x, y ∈ X?
  27. V

    Matlab Plotting Points and a Cubic Polynomial that passes through them

    Homework Statement We were given a tutorial to complete which I did complete. Now the question is: By modifying the appropriate lines in your script file, find the values of a, b, c, and d so that the cubic polynomial  y = ax3 + bx2 + cx + d  passes through the (x, y) pairs (-1, 3), (0, 8)...
  28. twoski

    I Getting Points Inside Of A Polygon

    Let's say we have a somewhat complex polygon shape. We know the list of 2d vectors that make up its border loop. Now let's say i want to create a list of points within this polygon. Currently i am using ray traces to create a grid of points that fall within the polygon. I'm certain there is...
  29. S

    Phase difference between points on wall

    Homework Statement Parallel water waves of wavelength 10 m strike a straight sea wall. The wavefronts make an angle 30o with the wall. What is the difference in phases between the waves at two points 5 m apart along the wall? a. 30o b. 45o c. 90o d. 156o e. 180o Homework Equations Δφ = Δx / λ...
  30. Edge5

    B Quartz vs. Glass -- why do they have different melting points?

    Why quartz has a higher melting Temperature than glass? Which one is harder and why?
  31. CrosisBH

    Finding an area of a triangle formed by three points

    Homework Statement P(3, 0, 3), Q(−2, 1, 5), R(6, 2, 7) (a) Find a nonzero vector orthogonal to the plane through the points P, Q, and R. (b) Find the area of the triangle PQR Homework Equations A = \frac{1}{2}|\vec{AB}\times\vec{AC}| Source...
  32. E

    Puzzled by how the Voltage is the same across different points

    If this is better for the HW section please tell me, sorry about that. So Voltage is the change in potential. I'm puzzled by how potential in circuits is the same along different points until we reach a resistor - at which point the potential changes. As in, if we take two points before a...
  33. K

    I Tangent spaces at different points

    How do you know whether two points ##p## and ##q## of a manifold have the same tangent space? If the two tangent spaces are equal, then the vectors in the two tangent spaces are exactly the same. I suspect that it's equivalent to picking a vector at ##p## and dragging it to ##q## and the vector...
  34. A

    MHB Finding border points and then interior points

    I am working on a classical real analysis problem as follow: The answers from solution manual are respectively $ int (A) = \emptyset$ and $bd (A) = \{0\} \cup \{ \frac{1}{n} | n \in \mathbb N \}$. And here are my textbook's definition of interior point and border point: And then there is...
  35. OWN9494

    Misc. Lifting vehicles with 4 points of contact

    Hello all. Just a quick fyi...I have never taken a physics class although I did want to in high school (many years ago). I am just looking for an answer to a very complicated (yet simple looking on the outside) problem I am having. In my job (towing 13 years) I use physics daily even though I...
  36. M

    Prove that five points are collinear

    Homework Statement There are five points on a plane. There is no line that passes trough exactly two points. Prove that five points are collinear. Homework Equations - The Attempt at a Solution I am just trying to confirm that my proof is correct. I am trying to prove this by contradiction...
  37. K

    I Why does LHC have 8 interaction points?

    Hello! I attached a picture of the LHC main rings. I see 8 interactions points labeled, even if there are only 4 experiments (and the other 4 points don't even intersect). What are these 4 other points? Thank you!
  38. E

    MHB Find the distance between points C and D if the height of the tree is 4m

    So the question is...From point C on the ground level, the angle of elevation to the top of a tree is 30 degrees. From point D, which is closer to the tree, the angle of elevation is measured to be 45 degrees. Find the distance between points C and D if the height of the tree is 4m. I know...
  39. K

    I Tangent spaces at different points

    How do you know if two given points on a manifold have the same tangent space? Checking if a vector does not change when transported from one point to the other is enough?
  40. Kenneth1997

    Directional derivatives at critical points

    x*abs(y)*(y+x^2+x)=f(x,y) so, on normal points they are tangent vectors on some point in the chosen direction. how about in critical points, where there shouldn't be any on a geometrical standpoint? can i say they exist if i get them with the definition? or the result i get has no value? like...
  41. Phys pilot

    Critical points of a diff eq system

    Homework Statement I have to calculate the critical points of the following system. $$x'=cx+10x^2$$ $$y'=x-2y$$ The Attempt at a Solution So I solve the system $$cx+10x^2=0$$ $$x-2y=0$$ So if $$x=2y$$ I have $$2yc+10*4y^2=2yc+40y^2=y(2c+40y)=0$$ and I get $$y=0$$ and $$y=-\frac{c}{20}$$ f I...
  42. S

    MHB Need formula for solving ellipse radius with equal spacing points

    I'm trying to build an oval bicycle wheel and need a formula to calculate the radii so that I can use the results to calculate the length for each spoke. See diagram for details. Hope someone can help.
  43. H

    Prove that there exists a graph with these points such that....

    Homework Statement Let us have ##n \geq 3## points in a square whose side length is ##1##. Prove that there exists a graph with these points such that ##G## is connected, and $$\sum_{\{v_i,v_j\} \in E(G)}{|v_i - v_j|} \leq 10\sqrt{n}$$ Prove also the ##10## in the inequality can't be replaced...
  44. T

    B Another spaceship and two points question....

    Sorry if this has been done elsewhere but I haven't seen it. Case: At the start a craft with a pilot is collocated at a position with a clock A with a second clock B one light hour away synchronized with A. All are motionless relative to each other. Clock A reads noon and B reads 11am. Good...
  45. Charlie Cheap

    Automotive Points ignition output voltage and length?

    As the go-to-guy for first generation 6-cylinder Mustangs, I have an unusual question. With a carburetor type engine, operation at 1000 to 5000 rpm, is a modern electronic ignition truly better than a hot points system? After studying both types it seems newer ignitions make a hotter spark but...
  46. M

    A Fine structure and fixed points

    I apologize for creating a new thread which has significant overlap with two other ongoing threads ("Quantization isn't fundamental", "Atiyah's arithmetic physics"). But both those threads discuss theories or paradigms of extreme breadth, whereas here I want to focus on a very specific bundle of...
  47. F

    Stability of singular points in a discrete control system

    Homework Statement Give an example of a non-linear discrete-time system of the form x1(k + 1) = f1(x1(k), x2(k)) x2(k + 1) = f2(x1(k), x2(k)) With precisely four singular points, two of which are unstable, and two other singular points which are asymptotically stable. Homework Equations J =...
  48. Y

    MHB Power Series (Which test can i use to determine divergence at the end points)

    Hello, I was given f(-4x)= 1/(1+4x), and I used the geometric series to find the power series representation of this function. I then took the limit of (-4x)^k by using ratio test. The answer is abs. value of x. So -1/4<x<1/4 I then plugged in those end points to the series going from k=0 to...
  49. M

    MHB Intersection points of two quadratic functions

    Justify the following by using table, graph and equation. use words to explain each representation f(X) = 2 x2 - 8x and g(x) = x2-3x+ 6 the points (-1,10) and (6,24)
  50. S

    Trouble in understanding a few points of colligative properties

    I am having a little trouble in understanding a few points of colligative properties. Any help will be appreciated. First, let's consider RLVP. We know that addition of a non-volatile solute decreases the vapor pressure of a pure volatile solvent. However, I am getting confused between the...
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