Just a word of caution with the equation above. All units have to be in one unit or another. I.E Metres per second. I find if you are using nautical miles per hour (knots) (as a TAS) then an easy and general rule of thumb divide the TAS by 2 before squaring which gives you rough speed in m/s. Another quick tip, unless stated otherwise I assume G = 10. Makes the calcs a lot quicker and easier. and yes you are correct in thinking:
TAS^2/(TAN bank angle
x G)
Tacho