When I run the program example (9.20) ex_acosd.nxc I get the error : Undefined Inditifier acosd.
Should I set a special switch to compile this example correct?
All these functions require the enhanced NBC/NXC firmware so you need to have it installed on your brick and you have to tell the compiler to target the enhanced firmware. That is via -EF on the command line or by checking the "Enhanced Firmware" checkbox on the NBC/NXC tab of the Compiler page in the Preferences dialog.