Help with matlab program for cos(x)

[baznguy]

Homework Statement

The function cos(x) can be approximated using the following series expansion:

Write a MATLAB function called seriesCos that takes a single scalar argument, x, uses the above formula to compute cos(x), and returns the result. Your function should use a while loop and continue adding terms to the series until the absolute value of the difference between successive iterations is less than 1.e-6. MATLAB functions that may prove useful include factorial() and abs().

Homework Equations

i can't get it to work and I'm not sure what I am doing wrong.It's not going through the loop or anything

The Attempt at a Solution

function y=seriesCos(x);
%calculate cos(x) through a series
%user call seriesCos(x,n)
%x is number to evaluate n is desire cycles through series
x=input ('Enter x to be evalute: ');
ser=1;
sum=0;
n=1;
er=0.0;
while er>=1e-6
an=(-1)^n*x^(2*n)/(factorial(2*n));
sum=ser;
ser=sum+an;
n=n+1;
er=abs((ser-sum)/(ser));
end
disp (ser)
disp (er)

 

[iamalexalright]

look at the line in which you start the while loop and you should see something wrong

Spoiler

what is er defined to be?

 

[CompuChip]

You are right, it's not going through the loop, because you are telling it not to:

er=0.0;
while er>=1e-6 
 ...

I suggest setting er to something larger than 1e-6 to start with :P