nesmira
Sep 23, 2009, 04:29 PM
Prove the identity!
Cos (pi/2 - x) = sin X
Unknown008
Sep 24, 2009, 07:45 AM
Use your formulae:cos(A-B) = cosAcosB + sinAsinB
cos(\frac{\pi}{2} -x) = cos(\frac{\pi}{2})cos(x) + sin(\frac{\pi}{2})sin(x)
cos (\frac{\pi}{2}) = 0
sin(\frac{\pi}{2}) = 1
cos(\frac{\pi}{2})cos(x) + sin(\frac{\pi}{2})sin(x) = (0)cos(x) + (1)sin(x)
That's all, it's almost finished. You only have to simplify.
I hope it helped! :)