Question

4.f(x)=sinx/√1+tan^2x+ cosx/√1+cot^2xis constant in which of following interval -
(A)[о,π/2]

(B)[π/2,π]

(C)[ π,3π/2]

(D)[3π/2,2π]
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Answer 1

Please mention the photo I can't understand the above mentioned question.