Sin u = 5/13 and pi/2<u<pi.
Find Sin (u/2); How do you determine the sign (positive or negative) for the value?
Using that information find cos (u/2): I have sqrt(26)/26. Is this positive or negative? How do I know?
sin u =5/13 and pi/2<u<pi
so find cos u = -12/13 as it is in 2nd quadrant.
use cos u= 2 -1 to evaluate cos u/2.
you take only positive value as it is in 1st quadrant.
using that you can find sin u/2 also.
since u/2(pi/4<u/2<pi/2 ) is in 1st quadrant
both cos u/2 and sin u/2 are positive.