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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 D

Explanation:

We have ,

  cos2θ+sin2θ+1=01sin2+sinθ+1=0

 sinθ=1(sinθ2)θ=3π/2

   θ(5π4,7π4)