asin (arc sine, inverse [sin]e) is a command made available in the [Tclx] extension (or in the ::tcl::mathfunc [namespace] from [Tcl 8.5] onwards). It accepts the same arguments as the [expr] function, and can take expressions as arguments. ---- !!!!!! %| [Category Command] | [Category Function] | [Category TclX] |% !!!!!!