Question

cos 40+cos 80+cos 160+cos 240 = ?...want a step-by-step answer...40,80,160,240 are degrees...

Answer 1

what do you want to do with it just simplify?

Answer 2

ya..

Answer 3

Okay.
Evaluate cos at those respective degrees and then add them up, right?

Answer 4

Wolframalpha gave me -1/2

Answer 5

I got -0.5 also at W/A but idk y...

Answer 6

answer..is -0.5,but we can't do it by evaluation,I mean we can't remember those values in exam.

Answer 7

I want a step-by-step answer

Answer 8

http://answers.yahoo.com/question/index?qid=20130425100013AA8W5Da

Answer 9

this one's so long....

Answer 10

lolz

Answer 11

A minor point, but an important one: unless you state that those numbers are degrees, then they're assumed to be radians. Did you mean degrees?

Answer 12

@dkco ,sorry for not mentioning,those are degrees