Prove the following:
L.H.S. =
= ...(i)
R.H.S. =
= ...(ii)
From (i) and (ii), we have
L.H.S. = R.HS.
If cos (A + B) sin (C - D) = cos (A - B) sin (C + D)
Show that: tan A tan B tan C + tan D = 0