Convert the following point from rectangular coordinates to

Convert the following point from rectangular coordinates to cylindrical coordinates. Give any angles in radians (6,6,8)
I have an answer but not sure how to convert to radians with calculator
(6sqroot2, ?,2). Theta equals tan6-1 (6/6). Answer would be either 7pi/4 or 7pi/2?

angle = tan-1(6/6) = 1 = 45 degrees = 45 *pi/180 radians = pi/4 radians r = sqrt(6^2+6^2) = 8.485 in cylindrical coordinates r = 8.485 angle = pi/4 radians z = 8