stoutfellow (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
stoutfellow) wrote2019-08-22 04:10 pm
stoutfellow) wrote2019-08-22 04:10 pm
Entry tags:
Oops!
Today, in Linear Algebra, I made a mistake.
I was at the board, working a problem from the book. It was an exercise in Gaussian Elimination. Doing GE by hand is a long and tedious process, and it's easy to make mistakes, which will then proliferate and ruin the entire calculation. So, of course, I did so. When I reached the end, the solution was rather ugly, which should have tipped me off. At that point, one student raised his hand and said, "Um, I'm sorry to say this so late, but I think you made a mistake. I did it another way and got a much nicer answer." One of the other students indicated agreement.
I went back to the beginning of the calculation - fortunately, still on the board - and detected the error. The first student apologized again; I turned and bellowed, "Never apologize for being right!" We continued with the correction (I added commentary on the art of solving problems from a textbook) and achieved a much more satisfactory result. The second student asked, "There's only one solution, right?" I said something about bound variables, which amounted to "Right!". He then replied, "I got a different answer..." (He rechecked, and found that he, too, had made a mistake.)
It's a bad thing for an instructor to make an error in class. Some errors are retrievable; the students seemed in good humor when I dismissed them.
[The class met at 12:30, i.e., just after lunch, and the room was too hot; something was wrong with the A/C. My goof, and its consequences, apparently served to avert student somnolence, so that's another good thing. I reported the situation to the secretary, and she leapt into action. I'll be in that room next on Tuesday; hopefully things will be better by then.]
I was at the board, working a problem from the book. It was an exercise in Gaussian Elimination. Doing GE by hand is a long and tedious process, and it's easy to make mistakes, which will then proliferate and ruin the entire calculation. So, of course, I did so. When I reached the end, the solution was rather ugly, which should have tipped me off. At that point, one student raised his hand and said, "Um, I'm sorry to say this so late, but I think you made a mistake. I did it another way and got a much nicer answer." One of the other students indicated agreement.
I went back to the beginning of the calculation - fortunately, still on the board - and detected the error. The first student apologized again; I turned and bellowed, "Never apologize for being right!" We continued with the correction (I added commentary on the art of solving problems from a textbook) and achieved a much more satisfactory result. The second student asked, "There's only one solution, right?" I said something about bound variables, which amounted to "Right!". He then replied, "I got a different answer..." (He rechecked, and found that he, too, had made a mistake.)
It's a bad thing for an instructor to make an error in class. Some errors are retrievable; the students seemed in good humor when I dismissed them.
[The class met at 12:30, i.e., just after lunch, and the room was too hot; something was wrong with the A/C. My goof, and its consequences, apparently served to avert student somnolence, so that's another good thing. I reported the situation to the secretary, and she leapt into action. I'll be in that room next on Tuesday; hopefully things will be better by then.]