add more help text

cmd/modInverse.go

@@ -48,10 +48,12 @@ func modInverse(cmd *cobra.Command, args []string) {
 
 // modInverseCmd represents the modInverse command
 var modInverseCmd = &cobra.Command{
-	Use:   "mod-inverse",
+	Use:   "mod-inverse -g N -m N",
 	Short: "Compute a modular inverse",
-	Long:  `Compute a modular inverse.`,
-	Run:   modInverse,
+	Long: `Compute a modular inverse.
+
+Given a base g and modulus m, compute a value x such that gx = 1 (mod m). A solution only exists if g and m are coprime.`,
+	Run: modInverse,
 }
 
 func init() {