MATLAB: How to find the 3 roots of the equation 2sinx=x

solvevpasolve

I entered as following: syms x vpasolve(2*sin(x)==x, x)

Matlab gives one answer only ans=0. But the correct answer should have 3 solutions. x=-1.89549, or x=0, or x=1.89549

Please help. Thanks

Best Answer

syms x 
fplot(2*sin(x)-x)
grid on 
vpasolve(2*sin(x)==x,x,2)
vpasolve(2*sin(x)==x,x,-2)
vpasolve(2*sin(x)==x,x)

Remark: See the graph guess the nearest root and get the exact root results

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syms x
disp('A =')
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A=sinc(x);

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MATLAB: Displaying a more precise answer when using diff()

In your code you have asked for the derivative of the constant 1, and of course its derivative will be zero. You need to find the expression for the derivative of f with respect to x and only then evaluate it for x = 1. That is, do diff(f,x) first, then find its numerical value at x = 1.

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MATLAB: Displaying a more precise answer when using diff()

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