Question

find the exact value of cos(pi) + cos(3pi)

Answer 1

You can find cos(pi) and cos(3pi) using the unit circle

Answer 2

http://www.google.com/imgres?imgurl=http://etc.usf.edu/clipart/43200/43215/unit-circle7_43215_lg.gif&imgrefurl=http://etc.usf.edu/clipart/galleries/617-unit-circles&h=225&w=225&tbnid=QVAM-3eg4ofZjM:&zoom=1&tbnh=186&tbnw=186&usg=__G5ez3VkOtBLFkgT88lzlRc_y2Qs=&docid=6bg0putUtYyCxM&itg=1&sa=X&ei=rYQLVPC3CYnD8gHwnIGoDw&sqi=2&ved=0CG8Q_B0wCg

Answer 3

Find pi
on there and then you can find cos(pi)
by just looking at the x-coordinate

Answer 4

so what is cos(pi)?

Answer 5

cos(pi) = -1?

Answer 6

ok
can you find cos(3pi)?

Answer 7

is it -1 as well?

Answer 8

yep

Answer 9

so cos(pi) is -1 and cos(3pi) is also -1
and then the question is asking you to do -1+(-1)

Answer 10

so the answer is -2? but isnt that the approximate value and not the exact value?

Answer 11

-2 is an integer
it is an exact form

Answer 12

okay thank you very much.