What should I do if I found too many typos after my Ph.D. thesis being approved but before my oral defense in mathematics? I am doing my Ph.D. in mathematics and did not have my thesis carefully proofread before submission (which is definitely a mistake that I wish to correct). My thesis was approved after submission and I am now preparing for the oral defense.

Now as I reread my thesis in detail, I found that there are too many typos (probably more than five per page). Some are negligible, but some are essential. For example, I wrote "&lt;" instead of "less than or equal to") in the conclusion of a proposition. Another example is that I quoted a wrong theorem number in a proof. I even wrote a same lemma with the same proof twice. One referee complains about the misprints in his/her report, but s/he still considers the thesis tolerable as a whole. But now I feel all those careless typos very annoying and they make the thesis much less readable.

Now I am seeking suggestions on what I should do. Should I correct all known typos and give each committee member a copy of the revised thesis on my defense? Is there any other thing that I can do right now?
Talk to your advisor. 

When I defended, my committee came back with a number of such corrections to be made. I made them and they signed off. Then the thesis editing office took the document and came back with even more corrections. I made those, and eventually they signed off. Trust me, you aren't the first to deal with this problem, and likely not the first that your advisor has seen.