MATLAB: Find all the roots of the following function in the interval 0.5<=x<=5. f(x)=(2/x-x)cos(x)+0.0119. Each root must be accurate to a minimum of six significant figures. I really can't figure it out.

roots

I need to write a code using bisect or false position to find all the roots of this function. I am lost. Don't know how to do it.

Best Answer

Plot the graph for f(x) in [0.5:5], choose intervals that contain only one of the roots and use MATLAB's fzero together with the intervals as initial condition to locate the roots exactly.

Best wishes

Torsten.

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MATLAB: Using roots function to find values

try :

 F=[3 -5 0 10];
 r=roots(F);

MATLAB: F(x) = (sin(x))^0.5

Austin - in your question, you indicate that the domain for x is [-10,10], yet you have

 x2=-10/pi:2*pi:10/pi;

which (when corrected for 2*pi) only returns am array of two elements

 -3.1831       3.1001

of the domain for [-10/pi, 10/pi]. Instead, use linspace to generate a linearly spaced vector/array of elements for your domain. For example,

 x = linspace(-10,10,2000);

will generate 2000 elements that are linearly spaced in the interval [-10,10].

Now you want to only plot those values of y that are real, and ignore those that are complex (with non-zero imaginary components). The latter occur whenever sin(x) is negative. You can ignore these by setting them to NaN as

 y      = sin(x);
 y(y<0) = NaN;

and plot the square root as

 plot(x,sqrt(y),'color','blue','linewidth',2);

Try the above and see what happens!

Best Answer

Related Solutions

MATLAB: Using roots function to find values

MATLAB: F(x) = (sin(x))^0.5

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