how to convert cos(2*pi*f1*t).^2 wave into cos(2*pi*f1*t) wave?)

i want to convert cosine square wave back into cosine wave.. can any one guide me please?

[Jan]

What are the available inputs?

Answer 1

[Jan]

By taking the square root?

f1 = 23;
t  = linspace(0, 4*pi, 10000);
y2 = cos(2*pi*f1*t).^2;
y  = sqrt(y2)

But the sign is lost. If you do not have any addition information about the phase, there is no way to find out, which parts have been positive or negative before the squaring. But wouldn't it be simpler to calculate the values directly?

y = cos(2*pi*f1*t);

? What is the problem you have to solve? Maybe you have the values of y2 and want to fit the parameter f1, such that you can create the cosine values afterwards?