Delete first line from any text file ?

What command I can use to delete first line from any text file ?
Thk

awk 'FNR>1' myfile

or

awk 'FNR>1' myfile1 myfile2

sed 1d textfile

Thk very much for all reply.

And what command which I can calculate any number in operation

<command> "[calculate area]"

you mean like -
expr 2 \* 4
result would be 8

Thk very much..