sine approximation using a loop

https://grader.mathworks.com/courses/20611-cmpsc-200-section-003-fa20/problems/214057-sine-approximation-loop-selection-factorial/solutions/new?based_on=32876101

The link above should have my work on it could someone help explain what I am doing wrong.

[James Tursa]

Please post your code here and ask specific questions about it.

[Yogesh Bhambhwani]

%% Problem 3.2 Template

%{

test cases:

x = 0.2; N = 7; -> s = 0.198669330795061

x = 1.85; N = 4; -> s = 0.960597005280723

%}

function [s] = prob3_2(x,N)
% function [s] = prob3_2(x,N)
% takes a scalar angle measure x (in radians) and estimates sin(x) using
% the first N terms of an alternating series
format long
%edit below this line ---------------------

x = pi/2;
error = 1;
n = 1;
count = 0;
while error >= 1*(10^-3);
    count = count+1;
    terms(count) = (-1)^(count+1)*(x^n)/factorial(n);
    s = sum(terms);
    n=n+2;
    error = abs((sin(x)-s)/sin(x))*100;
end
disp(s)

%edit above this line ----------------------
return

Answer 1

[Walter Roberson]

x = pi/2;

That is overriding the user input about the value to find the sine of.

function [s] = prob3_2(x,N)

You never use the user input N

n = 1;

you have a variable named n which is confusing considering the input named N

while error >= 1*(10^-3);

You are proceeding until your error is in a certain range, but the problem requirement says

% takes a scalar angle measure x (in radians) and estimates sin(x) using

% the first N terms of an alternating series

so you are not intended to go until error is a particular range: you are to go until you have used a particular number of terms.

        error = abs((sin(x)-s)/sin(x))*100;

Is error a percentage, or is an absolute value?

What about the cases where sin(x) = 0 ? You would be dividing by 0, which is not going to give you a useful error measure.