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Sunday Puzzle correction: A lesson in trigonometry


OK, so hold on, Will. Before we totally wrap up this week's puzzle, we need to admit to a bit of a mistake that we made in one of our answers last week. I think you know what I'm talking about.

WILL SHORTZ, BYLINE: Yeah. Yeah. And when you say we, that's very generous, but it was my mistake.

RASCOE: So here is what happened.


SHORTZ: In math, what cosine is to sine.

ELIE DOLGIN: Inverse function.

SHORTZ: Inverse function is it.

RASCOE: OK, ah - so, as it turns out, that is not it. And y'all did not hesitate to give us a quick math lesson, specifically in trigonometry. Do you remember trigonometry, Will? I mean, I think I learned it either junior high or senior high or whatever high, but it was a long time ago. That's what I know. Do you remember that?

SHORTZ: Oh, I remember taking trigonometry, and obviously, I've forgotten part of it, too.

RASCOE: (Laughter) So we got a lot of emails on this, including one from Martha Hasting, a professor of engineering mathematics at Washington University in Saint Louis, Mo., so first off, what's the inverse of a function?

MARTHA HASTING: If two functions are inverses, that means that one reverses the action of the other.

RASCOE: And Professor Hasting said that the cosine function definitely does not do this for sine, so does sine even have an inverse function?

HASTING: There is a function which does always reverse the action of the sine function, and it's called the arcsine function.

RASCOE: All right, so I think I get it, or I'm going to pretend that I get it. Do you got it, Will?

SHORTZ: Oh, I got it. Yeah. I will try never to make that mistake again.

RASCOE: And to our listeners, thank you for keeping us on our toes. Transcript provided by NPR, Copyright NPR.

NPR's Puzzlemaster Will Shortz has appeared on Weekend Edition Sunday since the program's start in 1987. He's also the crossword editor of The New York Times, the former editor of Games magazine, and the founder and director of the American Crossword Puzzle Tournament (since 1978).
Lennon Sherburne