mike23 Jan 4, 2021:

cosine vs cosign cosine - a mathematical term; Not to be confused with: cosign – to sign a document jointly with another; to endorse, as for a mortgage
https://www.thefreedictionary.com/cosine
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The six trig functions are named sine, cosine, tangent, cotangent, secant, and cosecant. Many people confuse the spoken word sine with sign — you can’t really tell the difference when you hear it unless you’re careful with the context. You can “go off on a tangent” in some personal dealings, but that phrase has a whole different meaning in trig.

Cosigning a loan isn’t what trig has in mind, either. The other three ratios are special to trig speak — you can’t confuse them with anything else.
https://www.dummies.com/education/math/trigonometry/defining...

kasiamiron (asker) Jan 3, 2021:

Tak właśnie i to trzy razy. Książka poważna i wydawnictwo poważne, a wygląda jak błąd. Innego wyjścia chyba nie ma.

mike23 Jan 3, 2021:

W książce tak to zapisano?