T-89 not giving pi back as cos(-1)

[Tyrion101]

I have a cosine calculator problem, and it keeps coming up wrong. So I figured to test it would be to do cosine of -1 which should be pi, either symbolically or numerically but it doesn't come out with either. It either produces cos(1) or .540302. It used to give pi as the symbol or as the number. What did I change?

 

[sk1105]

Are you doing inverse cosine?

$arccos(-1) = \pi$

 

[Mark44]

I have a cosine calculator problem, and it keeps coming up wrong. So I figured to test it would be to do cosine of -1 which should be pi, either symbolically or numerically but it doesn't come out with either.

You should be using cos^-1, the inverse cosine function.

It either produces cos(1) or .540302. It used to give pi as the symbol or as the number. What did I change?

 

[Tyrion101]

Thanks! I'd hate to fail the course because of a stupid mistake like this!

 

[Mark44]

So I figured to test it would be to do cosine of -1 which should be pi

Thanks! I'd hate to fail the course because of a stupid mistake like this!

This mistake suggests a fairly serious flaw in your understanding of these trig functions. The sine and cosine functions never get above 1 or below -1, so it's not possible for the cosine of any real number to be $\pi$.

 

[symbolipoint]

Here is how to make sense very quickly:

$$cos(-1)=π$$ -----------------No. Too big for any cosine value.
and: Is that cosine function input in radians or in degrees?