While-end statement using factorial(),abs() and cos()

I am having trouble understanding what I need to accomplish in part c of this lab. This is my code so far.

if true%
  clear all; 
clc;
close all;
x=input('Enter a value for x (in radians): ');
threshold=input('Enter a threshold in the range (0,1): ');
while ( threshold < 0 || threshold > 1) 

fprintf('Incorrect input, please try again.\n'); 
threshold = input ('Enter a threshold in the range (0,1): ');

end

How would I that formula?? I already have the user input x and threshold value. I need to use a while loop to compare the value of mycos(x) and cos(x) until the difference between the two is less than or equal to the threshold value entered by the user. Then I need to determine the number of terms summed to achieve the accuracy...

Really not sure where to start on this part. The while loop it a lot more complex then the loop used for the previous step. Any help would be greatly appreciated.

while (mycos(x) - cos(x) <= threshold)<--really not sure how to start and why I need to use factoral, abs.

Answer 1

[Walter Roberson]

   mycos = inf;
   while abs(mycos - cos(x)) > threshold

Answer 2

[Dan]

Tank you very much Walter