two twos

[radosr]

Present a computation whose result is 5, being a composition of commonly used mathematical functions and field operators (anything from simple addition to hyperbolic arc-tangent functions will do), but using only two constants, both of them 2.
It is too easy to do it using round, floor, or ceiling functions, so these are not allowed.
Note: You can not use variables, like x. You can use square root and power, but squaring will cost you one "2" and other constant powers are not allowed.

 

[Novak]

sec(2 arctan 2) ?

cos x = (1 - tan^2 x/2) / (1 + tan^2 x/2)

 

[pathfinder]

5= sqrt( .2 ^ -2)

 

[Novak]

sqrt counts as another 2

 

[emil]

sqrt counts as another 2

sqrt use should be ok since only

... squaring will cost you one "2" ...

 

[euroazn]

(cosh(arcsinh(2)))^2 ?

 

[pruse]

sec(2 arctan 2) ?

this isn't equal to 5

 

[Novak]

this isn't equal to 5

sure, was too lazy to check. (cosh(arcsinh(2)))^2 is fine.