tanh x = 12/13
1) Calculate cosh x:
cosh² x = 1/(1-tanh² x) →→ 1/[1-(12/13)²] = 1/(1-144/169) = 1/[(169-144)169]
cosh²x = 169/25 and cosh x = + or - 13/5
2) Calculate sinh x
sinh x/cosh x = tanh x →→sinh x = (cosh x)(tanh x)
sinh x = + or - (13/5)(12/13) →→sinh x= + or - 12/5
From here onward you can calculate easily coth x, sech x, csch x