consider the problem as
use the compound angle identity keeping in mind that
if you think about where 90degrees is
you will see that the cos beween 0 to 90 (85) is the same length as the cos from 90 to 180 (95) just 5 degrees both sides of off 90degrees however in the I quadarent
the cos is positive and in the II quadarant the cos neg so they cancel out to zero