I am a new user of *Mathematica*. I want to solve the following equation 

    a*Tan[a] = Sqrt[(52.7531 - a^2)]

for `a`, where `a` is a real value. I used the `Solve` function, but I am not getting the right answer.

I tried,

    Solve[a*Tan[a] == Sqrt[(52.7531 - a^2)], a, Reals]

I am doing something wrong. Could anyone tell me what it is? 
Thanks in advance.