Answer:
ok I did this construction about a year ago but I think I can remember something so if it's not correct I hope you won't be mad with me ok so the first step draw a straight line measure the length then make an AC on both sides then stand on one side make an arc upstand on the other side make an arc upthen stand on one AC and make another ARK on top of the other one then stand on the other AC and make another ark on top of the other one then join the lines yeah I think that's the procedure