for q2) f(x) = sin x - cosx therefore f ' (x) = cosx + sinx therefore f' (x) is 0 at x = 3pi/4 also since sinx & cos x are +ve in first quadrant therefore it's clear that f ' (x) is +ve from 0 to 3pi/4 & -ve from 3pi/4 to pi therefore f(x) is increasing from [0,3pi/4] & decreasing from [3pi/4 to pi]
Moderation Team
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