what is the solution to cos^2 x/3 = 1? I can't seem to be able to plug this into the calculator

$$\\(cos\frac{x}{2} )^2= 1\\\\
0= 1-(cos\frac{x}{2} )^2\\\\
(sin\frac{x}{2})^2=0\\\\
sin\frac{x}{2}=0\\\\
\frac{x}{2}=n\pi \qquad n\in Z \;\;$(N is an integer)$\\\\
x=2n\pi$$

I just realised that the question in your title is different from your question in your post  

This is how you have to do it with the calculator here:

Enter it like so: (Note: Use your keyboard to put the = sign into the equation.  Don't press the = sign on the calculator until after you have entered the whole equation.)

Press Enter or the = sign and you get the following output:

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