MATLAB: How to find the first 3 roots of sin(x)+0.5=0 bigger than zero? (Multiple roots)

multiple rootsperiodic function

Without using fzero function and without plotting the sin(x)+0.5 to find where the plot coincides with the x-axis, is there another way to obtain the first 3 roots of sin(x)+0.5=0?

Thanks Efe

Best Answer

Efe, that looks like a trick question... sin(x)+5 cannot be equal to zero, since sin(x) is between -1 and +1.

Related Solutions

MATLAB: Index exceeds matrix dimensions. in for loop !

for i=1:Np
    x(: , i+1) = f(x(: , i) , U(:,i));

That needs to access up to the Np'th column of U

    Cost ([1;1;1;1;1;1] , randn(3,1) , [1;1;1] , 2 , 0.01)

but U only has one column.

The Np that you pass in (2) should not exceed the number of columns of your second parameter.

MATLAB: Find roots

The key to this problem is that there is one root in each interval [n*pi,(n+1)*pi]. I'm going to assume that L > 1, otherwise the region near the origin is a special case.

function beta = find_beta(L,nRoots)
f = @(x) x*cot(x)+L-1;
beta = zeros(nRoots,1);
% A small offset is needed to avoid the asymptotes.
smallOffset = 1e-12;
for i=1:nRoots
    beta(i) = fzero(f,[i*pi+smallOffset (i+1)*pi-smallOffset]);
end

Best Answer

Related Solutions

MATLAB: Index exceeds matrix dimensions. in for loop !

MATLAB: Find roots

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