# sqrt(x) is sqare root, x^(1/2);
# sqrt(x_) := If(x==1, 1, If(x== -1, i, If(not(isnumber(x)), x^(1/2) )));


sqrt(1/x_):=1/sqrt(x);
sqrt(x_^2):=x*csgn(x);

sqrt(0.25):=1/2;
sqrt(-1):=i;
sqrt(1):=1;
sqrt(4):=2;
sqrt(9):=3;
sqrt(16):=4;
sqrt(25):=5;
sqrt(36):=6;
sqrt(49):=7;
sqrt(64):=8;
sqrt(81):=9;