UPSEE Solved Model Paper 3

∵ cos7x≤cos2x and sin4x≤sin2x On adding Eqs. (i) and (ii), we get
⇒ cos7x+sin4x ≤ 1
But given, cos7x+sin4x = 1
Equality holds only if cos7x = cos2x and sin4x = sin2x
Both are satisfies by x = ± π/2, 0