Integral of cos x^2

[nasi112]

Why my calculator says

\(\displaystyle \int_{-1}^{1} \cos x^2 \ dx \approx 1.999939\)

While the correct answer is

\(\displaystyle \int_{-1}^{1} \cos x^2 \ dx \approx 1.809048\)

I thought that calculators are designed to give a good approximation!

 

[Dr.Peterson]

Why my calculator says

\(\displaystyle \int_{-1}^{1} \cos x^2 \ dx \approx 1.999939\)

While the correct answer is

\(\displaystyle \int_{-1}^{1} \cos x^2 \ dx \approx 1.809048\)

I thought that calculators are designed to give a good approximation!

What kind of calculator is it? Can you show a picture of the screen with what you entered?

My suspicion is that it is in degree mode; see here.

 

[nasi112]

Oh my god. This is the thousand time, I made a mistake just because my calculator is set to the degree mode.
?

Thank you a lot Dr. Peterson.