I was enlightened by this article, especially after being scared off trig functions at school. I was even more enlightened when I punched in cos (1) into my calculator, a Casio fx-85GT PLUS which does have a cosine button, and got 0.9998... instead of 0.54... After an hour's bafflement I realised I needed to shift the set-up to radians, whereas I'd never got beyond degrees at school. Great, something more I've learnt. Purely as a matter of curiosity though, is it possible to come up with a power series that does as neatly converge on a value in degrees?

Chris G

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