i entered in my calculator and the answer was . the book's answer is .
i also did >Frac on my calc and it just showed the decimal form again, not the fraction form. is there a way to transform the decimal answer into the fraction answer?
Nevertheless, things like are things you should know.
you should know the value of trig functions at: and any integer multiple of those, and even any 1/2-multiple of those
for other regular fractions, those with no irrational numbers in them, your calculator should be able to handle it
there are memory techniques for memorizing the value of the trig functions of these special angles, so if that's what you're trying to avoid by using your calculator, it's not necessary