How can i do inverse trigonomic functions on a TI-30x IIS calculator?

Im doing second and cosecond and cotangent funtions in cl. i get it but how do i put for example Csc(2pi/9)? i know how to put Cos(2pi/9) and i know how to switch to rad mode rather than deg mode but i need help on that part with the inverse trig funtions?