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