“徒劳的”用英语怎么说

假装系统完美无疵是徒劳的。It would be idle to pretend the system is perfect.祈祷天气转变是徒劳的.It's no use praying for the weather to change.他们想方设法地使她高兴, 但那是徒劳的.They endeavored to make her happy, but in vain....