# Questions tagged [desmos]

A service that has several calculators and teaching material for Mathematics, with its most prominent feature being a graphing calculator that is available as an app and on a website.

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### How do I simulate a beam/particle bouncing off the inside of an ellipse in Desmos? [closed]

I have graphed an ellipse based on two focal points locked to the x-axis. I'm trying to figure out how to make the beam I made inside the ellipse bounce off of the inside surface and change trajectory,...
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### How to add labels into Desmos [closed]

Hi I believe this is Desmos 3d how to add labels into my project for any of my equations? I want to write notes underneath how to do it?
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### How should I keep arc length equal between multiple points on a parametric curve?

I made this thing in desmos: https://www.desmos.com/calculator/na9sehjskk The distance between points changes depending on the speed of the points. Is there a way to keep the distance between them ...
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### Why does Desmos give a small, nonzero value for $\sin(5\pi/6) - 1/2$?

I type $\sin(5\pi/6)$ and it says $0.5$, which is completely normal. However, when I add "$-1/2$," the result is $−5.5511151231×10^{-17}$. Why is it happening and am I doing something wrong? ...
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### Randomly Generating Real-Rooted Polynomial Equations

I need a simple function to generate real-rooted polynomial functions to demo my Desmos Aberth-Ehrlich rootfinding implementation. My current function is as follows: Let $n \in \mathbb{Z}^+$ be the ...
1 vote
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### $x^x$ graph freaks out

So I was goofing around in desmos when I plugged the function $f(x)=x^x$ And noticed that desmos shows only the positive part of the graph. Why does this happen. The function has real values. Can you ...
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### Desmos not plotting the obvious inequality correctly? [closed]

I was checking the subadditivity of the function $f\colon x\mapsto \min(1, x)$, i.e., whether $f(x + y)\le f(x) + f(y)$ and was expecting that the entire first quadrant would be colored. However, the ...
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### Graphing $(\lfloor x \rfloor + \lfloor1-x\rfloor)$

$\lim_{x\to0+}(\lfloor x \rfloor + \lfloor1-x\rfloor)$ $\lim_{x\to0-}(\lfloor x \rfloor + \lfloor1-x\rfloor)$ I tried to solve by graphing $(\lfloor x \rfloor + \lfloor1-x\rfloor)$ Graph of the ...
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### Parametric equation of inward pointing half sin waves

Parametric equation of inward pointing half sin waves I can create a circle in red and I can create a sin wave that goes around a circle in green. Parametric equation: ...
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### three-dimensional pixel

If we have some function, for example, $$y = ix^2$$, we can express that, (or any) function ($x,y$) with some kind of three-dimensional pixel ($t$ represents the pixel base whose length can be changed,...
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### How can you make a decimal point for a number display on Desmos?

I have this Desmos graph which is a number display. You type a button and that number gets displayed. I'm thinking about turning it into a calculator, but first I need a decimal point. (Also the ...
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### Why does Desmos not render graphs like this properly?

I was trying to show some students the graph of $y=4- \ln (2-x)$ today on Desmos. Unfortunately we can see from the picture below that the graph does not render correctly around the asymptote and ...
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### Desmos and Wolfram Alpha contradict: Is $|1+x| \ge 1 - |x|$ true for all $x$?

Is $|1+x| \ge 1 - |x|$ true for all $x$? When I solve this problem myself, I solved that it's true for all $x$. But when I put it into Desmos, I get this: https://www.desmos.com/calculator/vgxm3q1fso,...
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### Why does Desmos not plot $\sqrt{\frac{(x+y)^2}{2}} = \sqrt{x^2+y^2} + \sqrt{2}$?

I am working on the following problem: I need to find the points above the line $l:y=-x$ for which it holds that the distance to $l$ is $\sqrt{2}$ greater than the distance to the origin. I worked out ...
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Why does Desmos draw different perimeters for the graphs of $$r=\cos(2\theta)$$ and $$r\le\cos(2\theta)$$ (2 leaves versus 4 leaves)? Why do the numbers of leaves differ? $r=\cos(2\theta)$ $r\le\cos(... 0 votes 1 answer 274 views ### How to graph series in Desmos$f\left(x\right)=\sum_{n=1}^{x}nb-f_{1}\left(f\left(x-1\right)\right)$$$f\left(x\right)=\sum_{n=1}^{x}nb-f_{1}\left(f\left(n-1\right)\right)$$ $$b=2$$ $$f_1(x)=x^2$$ $$f(1)=b$$ How can I define this whole series in Desmos? 0 votes 1 answer 116 views ### How can i make Desmos equations only visible, if a variable is less than 0? [closed] Say i have some variable k that I can change, and an equation. How do I make the equation invisible, if, for example, k<0 is ... 4 votes 5 answers 225 views ### Discrepancy in definite integral$\int_{0}^{2\pi}\frac{1}{10+3\cos x}dx$using Desmos I was trying to calculate the following definite integral of a function$f(x)$: $$\int_{0}^{2\pi}\frac{1}{10+3\cos x}dx$$ After some effort, I managed to find the following antiderivative: $$F\left(x\... • 41 3 votes 0 answers 100 views ### Error in desmos while computing \int_{-\infty}^{\infty}e^{-x^2}dx When I was computing this integral \int_{-\infty}^{\infty}e^{-x^2}dx on Desmos I was getting correct answer as \sqrt \pi. But when I started to change the limits of the integration something ... • 99 0 votes 1 answer 53 views ### Skew with Sgn(x) yields unwanted signed line segments I'm using Desmos to visualize a concept, but I'm not getting what I expect. Assume we start with a morphed circle, in green, focusing only on the positive y values. We want to skew the green equal to ... • 111 0 votes 3 answers 229 views ### Negative integral but positive function? So I was in the search for a general formula of$$\int_{-\infty}^\infty\frac{1}{1+x^n}dx$$I haven't found one yet, but I realized that for odd n this is 0. For even n, I decided to try a few ... • 6,519 0 votes 1 answer 354 views ### How would I accurately simulate orbital motion in desmos? [closed] Basically, I've been wanting to make a map of a fictional solar system which moves accurately. I have a circle to represent the parent star, a circle representing the planet, which is moving around a ... • 111 1 vote 0 answers 50 views ### Problem with plotting products of polynomials First, I typed x(x-1)=0 in Desmos and they showed the correct two lines. Then I changed the equation a bit into x(x-1)y=0 and they added a third line. But the previous two lines were gone. Expanding ... 0 votes 1 answer 1k views ### Desmos - plot x vs t instead of y vs x My physics students get very confused when they go from math class, where x is always (! stop that!) the horizontal axis, to physics where we put all kinds of things on the horizontal axis, including ... • 103 0 votes 1 answer 630 views ### Desmos assign operator (\rightarrow) assigning multiple times without click manually How do I assign a variabel automatically for n-times without clicking it n-times? I have this statement that I must click the red circled button in picture to assign updated value for variabel a: ... 0 votes 1 answer 726 views ### how to make a function, on Desmos, that, if h(x) is over n, then h(x) = f(x), but if h(x) is below n, then h(x)=g(x) I'm trying to represent on Desmos what my C++ Vex robotics flywheel control code would do, so that I can close in on an optimal constant in the equation without testing it on the robot, because that ... • 103 5 votes 1 answer 217 views ### Ellipse bounded between two lines and a circle Given two circles with radii \beta and \beta^{-1}, where \beta\geq1. Also, given two lines y=x\tan\alpha and y=-x\tan\alpha, where \pi/2>\alpha\geq0. I am interested in all ellipses ... • 1,910 1 vote 2 answers 242 views ### Visualising the order 2 rotational symmetry of the cube, about the midpoints of opposite edges. Given a cube am facing great difficulty in visualising rotation symmetries along the axis formed by the midpoints of diagonally opposite edges. Given two diagonally opposite edges, need consider the ... • 4,522 1 vote 1 answer 142 views ### Is the sinc function related to the Gamma function? I was just fooling around on Desmos and entered the function f_{n}(x)=\frac{n!}{x!(n-x)!}. When I set n=0, i.e. f_{0}(x)=\frac{1}{x!(-x)!}, I found that the resulting function looked strikingly ... 1 vote 1 answer 2k views ### Referencing a piecewise function in another function in Desmos produces error "You've already defined f(x) elsewhere"? I was trying to reference a piecewise function inside another function in desmos. For example, suppose I had the following:$$ f(x) = \left\{ \begin{array}{ll} |x+1| & \quad x\lt-1 \\ 0 & \... -1 votes 2 answers 83 views ### Desmos error? Incorrect evaluation of expression? This is the graph plotted by Desmos for the inequality$~\log_{0.2}\left(x^{2}-x-2\right)>\log_{0.2}\left(-x^{2}+2x+3\right)$Here, you can see that plotted interval is$~x \in [2, 2.5)~$but log is ... 2 votes 2 answers 141 views ### Is$\frac{x^2-3x-4}{-3x-15}\Big/\frac{x^2-16}{x^2-x-30}$defined at$x=6\$ or not?

If a number is in the denominator of a rational expression that itself is the denominator of another rational expression, such that the number causes the latter denominator to be undefined, then isn't ...