Question

Find an exact value.
cos(-7pi/12)

Answer 1

@hartnn

Answer 2

cos(-7pi/12)=cos(7pi/12)=cos(105)

Answer 3

cos(105)=-cos(75)

Answer 4

First, a question for you: What two simple fractions with denominators 3 and 4 respectively add up to 7/12?

Answer 5

so it would be C? @mustafa2014

Answer 6

3/3 4/4 @mathmale

Answer 7

@mustafa2014

Answer 8

3/3 and 4/4 add up to 2, so that could not be the correct combination of fractions.

Answer 9

My question is very relevant to solving this trig problem, in case you're wondering.

Answer 10

@mustafa2014 ?????????