What is the Algorithm for calculating a cosine of a number?

[rahul.6sept]

What is the Algorithm for calculating cosine of a number ?

Following posts moved from original thread:

• https://www.edaboard.com/threads/349902/

---------------

Dear All,

In the folowing code I'm not getting it correct.

function [cosVal] = maclaurinCos(x,n)
   
    % To Compute approximation of cos(x) using MacLaurin
    %     Series upto the n-th order term (x^n/n!)
     
    numerator = x.^[1:n];
    denom = cumprod(1:n);
    vec = [1, numerator./denom];
    terms=0;
    
    for i=1:n
        terms=((-1)^(2*n).*vec);
    cosVal=cumsum(terms);
    end
disp(['The value of Cos x is=   ',num2str(cosVal)]);

Regards,
Rahul

 

[andre_luis]

Re: What is the Algorithm for calculating the cube root of a number?

The function you posted above doesn't matches anyone of both the 2 algorithms ( Newton, Halley ) available at the link suggested. You have to ellaborate your questions, as well take into account what has already been answered.

 

[c_mitra]

Re: What is the Algorithm for calculating the cube root of a number?

Let me explain the algorithm:

x^3=a; we want to know x.

Follow Newton Raphson method:

x=a/(x^2); start with x=1;
x=a; this is the first iteration;
x_old=(1+a)/2; take the midpoint of the two;
x_new=a/(x_old^2); we get the next iteration;
see x_old and x_new are close enough; if yes then stop; else continue;
x_old=(x_new+x_old)/2;
(use x*x instead of x^2);

What is the above code (you have posted) supposed to do?

 

[rahul.6sept]

Re: What is the Algorithm for calculating cosine of a number ?

Hi Andre and C_mitra,

The cube root problem is solved. This is a different one. I want to determine the cos x using maclaurin series. I'm getting the output. But it is not correct.

Regards,

Rahul

 

[KlausST]

Re: What is the Algorithm for calculating cosine of a number ?

Hi,

Maybe a confusion with radians and degree?

Klaus

 

[c_mitra]

Re: What is the Algorithm for calculating cosine of a number ?

Sine and cosines are usually not computed using the standard series approximation because the series converges poorly (slowly). They are best computed using the Pade approximation (https://mathworld.wolfram.com/PadeApproximant.html).

If you still want to compute the series approx, find a recursion relation first. AND AS pointed out by KlausST, the argument must be in radians.