Question

I am currently working on a problem relating to trigonometric identities and I seem to be stuck. The question wants me to find sin(x/2) when cosx = -(12/13) in the interval (pi,3pi/2). I know that the eventual answer will be 5/sqrt26, however, I am not sure how to get there. Any help would be appreciated :).
Yes, I get that, but which formula do I rearrange to find sin(x/2)? Is it the one for sin2x? I am not too familiar with the formulas as I have been forced to learn trig identities on short notice.
you look up you half-angle formulas!

sin(x/2) = √((1-cosx)/2)
= √(1+12/13)/2)
and just simplify that.

Related Questions

Trigonometric Identities Prove: (tanx + secx -1)/(tanx - secx + 1)= tanx + secx My work so f... Which of the following are trigonometric identities? (Can be more then one answer) tanx c... The question wants me to find sin(x/2) when cosx = -(12/13) in the interval (pi,3pi/2). I know that... Use the given function value(s), and trigonometric identities(including the cofunction identities),...