matlab words no help needed

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Tyler Daines 2021-5-11

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编辑： Rena Berman 2021-6-29

I need to plot the sum of 2 sine curves. I can successfully plot (x,y1) and plot(x,y2), they are smooth curves, however when i try to plot(x,y) where y = y1+y2 the curve comes out like this? how do i fix this i dont know what i am doing wrong? Thanks

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Stephen23 2021-5-16

编辑：Stephen23 2021-5-16

Original question by Tyler Daines retrieved from Google Cache (unfortunately their deleted comments are not included):

https://web.archive.org/web/20210516175443/https://webcache.googleusercontent.com/search?q=cache%3A6xOVMwrjOj8J%3Ahttps%3A%2F%2Fwww.mathworks.com%2Fmatlabcentral%2Fanswers%2F827265-trying-to-plot-a-sine-sine-function-but-not-getting-a-smooth-curve

https://web.archive.org/web/20210516175823/https://www.mathworks.com/matlabcentral/answers/827265-matlab-words-no-help-needed

Trying to plot a sine+sine function but not getting a smooth curve

I need to plot the sum of 2 sine curves. I can successfully plot (x,y1) and plot(x,y2), they are smooth curves, however when i try to plot(x,y) where y = y1+y2 the curve comes out like this? how do i fix this i dont know what i am doing wrong? Thanks

Rena Berman 2021-6-29

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Answer 1

DGM 2021-5-11

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What you're looking at isn't meaningful. It's all just rounding error. You're essentially doing this:

y = sin(x) - sin(x);

I'm guessing there's some phase component that's not defined right yet, but I can't really guess at what you need it to be.

f = 2;
A = 1;
v = 1;
L = 1;
l = v/f;
B = (2*pi)/l;
w = 2*pi*f;
t = 0;
x = 0:0.0001:L;
z1 = A*sin(B*x - w*t);
z2 = A*sin(B*(L-x) - w*t);
y = z1+z2;
plot(x,z2); hold on
plot(x,z1);

For the future, please just paste your code using the code formatting tools. I had to retype all that and deal with the sub-pixel ambiguity differentiating the character '1' and 'l'.