My exam book is telling me the calculator should have a 1/x button, or a x-1 button but none of the online ones do. My one does but the battery died and new one not arriving - I am behind due. Is there an equivalent button I am missing.
The online calculator at https://www.calculator.net/ has a 1/x button.
Alternatively, use an xy button (as on the webcalc calculator on the home page) with y as -1.