Q. 295.0( 1 Vote )

Find the interval

Answer :

Given: f(x) = sinx + cosx

f’(x) = cosx – sinx

Now, for maxima or minima, f’(x) = 0


cosx – sinx = 0

sinx = cosx

Which gives us, as 0 ≤ x ≤ 2π

The points divides the interval 0 ≤ x ≤ 2π into three disjoint intervals, namely .

Now we will check the nature of f(x) in these intervals.

f’(x) > 0, if

Thus, f(x) is increasing in the intervals .


f’(x) < 0, if

Thus, f(x) is decreasing in .

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