how am i supposed to do this without a calculator?

Calculate the following trigonometric ratios.

sin (3pi/2) cos(3pi/4)

Question

how am i supposed to do this without a calculator?

Calculate the following trigonometric ratios.

sin (3pi/2)        cos(3pi/4)

anonymous · Answer

doesnt matter - i'm not meant to use one.. i have a casio fx-100au though   or a graphics one online (my ti 83plus is at home)

so i think i can get the first one with just the unit circle (-1)  but would i do the 2nd one the same way?

anonymous · Answer

oh
i thought that 180 was one pi
:0

anonymous · Answer

yea. most all trig uses 2pi. its stupid like that

anonymous · Answer

can you explain what you did then?

anonymous · Answer

sry 2pi = 360. my bad. 
just interchange pi with 180 and find it on the unit circle. if its biggerthan 360 or smaller than 0 add or subtract 360 untill it is between 360 and 0

anonymous · Answer

oh thats an awesome way of doing it... as long as it always works :)

anonymous · Answer

you can multiply the given radian by 180/pi and you can get its equal angle. :)

anonymous · Answer

it does. i promise