Prove that every monotonically increasing sequence which is bounded from above has a limit.
Why? This is YOUR homework. If you read the rules for this forum, as you are supposed to have done, then you know you must attempt it and show what you have done. One reason for that (other than the supremely important "you learn by TRYING") is to let us see what you have to work with. I know several different ways to prove this, depending upon which "axioms" you use for the real number system. But I don't know what axioms you are using.
Separate names with a comma.