Q12 of 96 Page 17

Write the interval in which f(x) = sin x + cos x, xϵ[0, π/2] is increasing.

f(x) = Sin x + Cos x, x ϵ [0, ]


f’(x) = Cos x – Sin x


For, f(x) to be increasing, it must have


f’(x) > 0


Cos x – Sin x > 0


Sin x < Cos x



tan x < 1


tan x < tan


x ϵ


Hence, the required interval is x ϵ .


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