1
$\begingroup$

I am unable to understand the graph plotting of $\sin (x) > \dfrac{-1}{2}$ on Desmos I have plotted Here is the enter image description here

I think the graph should be the shaded region between like this

Note second one is not the actual graph of previous function. I don't know to plot the above graphically so I have use an example. I hope I clear my point. Can anyone explain how it being plotted on Desmos? Or is this correct ? If yes how?

$\endgroup$
  • 1
    $\begingroup$ It is shading the $x$ points without regard for the $y$ points. $\endgroup$ – rubikscube09 Apr 30 '18 at 3:22
  • $\begingroup$ plot graph $y=\sin x$ then draw the line $y=-0.5$. Now look where graph of $\sin x$ is above the line $y=-0.5$ $\endgroup$ – Vasya Apr 30 '18 at 3:33
  • $\begingroup$ This is because you have no condition on $y$ $\endgroup$ – Thomas Andrews Apr 30 '18 at 4:26
3
$\begingroup$

Desmos is interpretting you request as find all $(x,y)$ such that $x$ satisfies $\sin(x) \ge -\frac12$. Hene for every $x$ that satisfies that condition, every $y$ is included. Hence we get all the vertical stripes.

Probably, you want to plot the following:

enter image description here

$\endgroup$
  • $\begingroup$ @Siong Thye Goh so desmos plotting is correct? I mean the graph you have plotted is different in theory as well? I expected my graph like yours. $\endgroup$ – Brij Raj Kishore Apr 30 '18 at 4:15
  • $\begingroup$ desmos is doing what what the user is telling it to do regardless of whether that is the user's intention. It is told to shade all $(x,y)$ as long as $x$ satisfies the condition. $\endgroup$ – Siong Thye Goh Apr 30 '18 at 4:18
  • $\begingroup$ I got it, it just a programmed. But sorry I am not able to make my question clear. Is the graph you plotted above is for $sin(x) > \dfrace{-1}{2} or it is a different function. I am not getting desmos involved into this. Or I am what I assumed is incorrect $\endgroup$ – Brij Raj Kishore Apr 30 '18 at 4:35
  • $\begingroup$ what is the original problem that you want to solve? should there be a variable $y$ in the first place? I am shading $\{ (x,y)| - \frac12 \le y \le \sin(x)\}$ while you plotted $\{ (x,y)| - \frac12 \le \sin(x)\}$ $\endgroup$ – Siong Thye Goh Apr 30 '18 at 4:39
  • $\begingroup$ Original problem is simply plotting the inequality $sin(x) > \dfrac{-1}{2}$ I have solved it on paper and found out the range which is $(2n\pi - \dfrac{\pi}{6} , 2n\pi+\frac{7\pi}{6})$ $n\in I$ $\endgroup$ – Brij Raj Kishore Apr 30 '18 at 4:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.