1) The solution of the equation cos2θ+sin2θ+1=0 , lies in the interval A) (−π4,π4) B) (π4,3π4) C) (3π4,5π4) D) (5π4,7π4) Answer: Option DExplanation:We have , cos2θ+sin2θ+1=0⇒1−sin2+sinθ+1=0 ⇒sinθ=−1(∵sinθ≠2)⇒θ=3π/2 ∴ θ∈(5π4,7π4)