how to make it on calculator or what is the value of tan^{2}?

To find tan^{2 }you first find tan, then you square that.

tan^{2} 30° = (tan 30°)x(tan 30°)

Tangent is a function, and tan^{2} have no value.

Of course Max is correct, there has to be an angle there. :)

or

(tan30)^2 = 1/3

The calc changes it to tan30^2 but that is ok :)

(tan(30))^2 = 0.3333333333337655

It should just be 1/3 so there is some rounding error.