More efficient "for i in array" loops

I Have a series of equations that need a range of input values, currently I am using a for loop like so.

Is there a more efficient way than having to write a for loop for each equaiton, but use the values from the array?

In the example cos_theta might be needed in mutliple equations later on. The full script has 10 or so loops that are just a bit messy

x = [1 2 3 4 5 6]
c = 1

for i = x
    cos_theta = [cos_theta, (1-((2*i)/c))];
end

for i = cos_theta
    theta = [theta, acos(i)];
end

Answer 1

[Alex Mcaulley]

Using your equations directly:

x = [1 2 3 4 5 6];
c = 1;
cos_theta = (1-((2*x)/c));
theta = acos(cos_theta);