Simple question

If\ f(x)=\sqrt{1-sin(2x)},f'(x) equals\\\ \\ a)-(cos x + sin x) for\ x\in(0,\pi/4)\\b)(cos x + sin x) for\ x\in(\pi/4,\pi/2)\\c)-(cos x + sin x) for\ x\in(\pi/4,\pi/2)\\d)(cos x + sin x) for\ x\in(0,\pi/4)\\

6 Answers

9
Celestine preetham ·

f(x) = | cosx - sinx |

1
dibya jagaddev ·

answer is c

13
deepanshu001 agarwal ·

i m wid cele s ans

1
sparkle2009 ·

Please let me know the flaw in my solution..

f'(x)=\frac{|cosx-sinx|}{cosx-sinx}\times -(sinx+cosx)\\\ \\ If\ x\in (\pi/4,\pi/2),tanx>1\ or\ cosx-sinx<0\\\ \\ so\ for\ x\in (\pi/4,\pi/2),f'(x)=cosx+sinx

11
Mani Pal Singh ·

It could be written as

\sqrt{sin^{2}x+cos^{2}x-2sinx cosx}

which is
|sinx-cosx|

now 2 cases arise

when sinx >cosx(∩/4,∩/2)................sinx -cosx
and cos x >sinx (0,∩/4)....................cosx-sinx

so f'(x) is cosx+sinx(∩/4,∩/2)
and -(sinx+cosx)(0,∩/4)

so answer is a and b

if its not matching then the answer given must ewrong

9
Celestine preetham ·

#5

no flaw

see #6 thats the approach

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