tRig0no|\/|3trî
cos x - cos y = - 2 sin (x + y)/2 sin (x - y)/2
•••
cos b - cos 3b
= -2 sin (b + 3b)/2 sin (b - 3b)/2
= -2 sin 2b . (- sin b)
= 2 sin b sin 2b
" Life is not a problem to be solved but a reality to be experienced! "
© Copyright 2013 - 2024 KUDO.TIPS - All rights reserved.
tRig0no|\/|3trî
cos x - cos y = - 2 sin (x + y)/2 sin (x - y)/2
•••
cos b - cos 3b
= -2 sin (b + 3b)/2 sin (b - 3b)/2
= -2 sin 2b . (- sin b)
= 2 sin b sin 2b