How do I find the zero crossings for a function sinx/x against x?

Question

Salreem 2021-7-11

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https://ww2.mathworks.cn/matlabcentral/answers/876368-how-do-i-find-the-zero-crossings-for-a-function-sinx-x-against-x

编辑： Matt J 2021-7-11

I have used the following code to plot

x=linspace(-90,90,10000);
y=sin(x)./x;
plot(x,y);
axis([-90 90 -1.5 1.5])
xlabel('x')
ylabel('y')
title('A GRAPH OF A FUNCTION Y=(SINX)/X AGAINST X')

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Answer 1

ANKUR KUMAR 2021-7-11

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在 MATLAB Online 中打开

Do you mean to find the x values which cooresponds to the zero in the y values?

I do not think you have zero value in y variables (It is close to zero, but not exactly zero).

This is an example using the round function so that it yields nearest integer value.

x=linspace(-90,90,10000);
y=round(sin(x)./x);
x_vals=x(y==0)
x_vals = 1×9790
  -90.0000  -89.9820  -89.9640  -89.9460  -89.9280  -89.9100  -89.8920  -89.8740  -89.8560  -89.8380  -89.8200  -89.8020  -89.7840  -89.7660  -89.7480  -89.7300  -89.7120  -89.6940  -89.6760  -89.6580  -89.6400  -89.6220  -89.6040  -89.5860  -89.5680  -89.5500  -89.5320  -89.5140  -89.4959  -89.4779

x_vals contains the x values which corresponds to zero in y values.

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Answer 2

Matt J 2021-7-11

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https://ww2.mathworks.cn/matlabcentral/answers/876368-how-do-i-find-the-zero-crossings-for-a-function-sinx-x-against-x#answer_744498

编辑：Matt J 2021-7-11

You can see analytically that the zeros will occur when the numerator sin(x) has a zero crossing, which will occur at non-zero integer multiples of pi. At x=0, L'hopital's rule readily shows you that there is no zero crossing there.