মান নির্ণয়

If n\mathrm{n} be the number of solutions of the equation cotx=cotx+1sinx(0<x<2π)|\cot \mathrm{x}|= \cot x +\displaystyle \frac{1}{\sin \mathrm{x}}(0<\mathrm{x}<2\pi) , then n ==

হানি নাটস

cotx=cotx+1sinx0<x<2π\mid \cot x \mid=\cot x+\cfrac{1}{\sin x} \,\,\,\,\,\,\, 0<x<2\pi
cotx\mid \cot x \mid is positive if cotx>0\cot x>0

Then,
cotx=cotx+1sinx\cot x=\cot x+\cfrac{1}{\sin x}
or, 1sinx=0\cfrac{1}{\sin x}=0
or, sinx= \sin x=\infty which is impossible.

cotx\mid \cot x \mid is -ve if cotx<0\cot x<0
cotx=cotx+1sinx-\cot x=\cot x+\cfrac{1}{\sin x}
or,2cotx=1sinx -2\cot x=\cfrac{1}{\sin x}
or, 2cosxsinx=1sinx\cfrac{-2\cos x}{\sin x}=\cfrac{1}{\sin x}
sinx0\sin x \ne 0 because x0x \ne 0

or, 2cosx=1-2\cos x=1
or, cosx=12=cos2π3\cos x=\cfrac{-1}{2}=\cos \cfrac{2\pi}{3}
or, x=2nπ±2π3x=2n\pi \pm \cfrac{2\pi}{3}
If n=1n=1
x=2π2π3=4π3x=2\pi-\cfrac{2\pi}{3}=\cfrac{4\pi}{3}
which is in the range (0,2π)(0,2\pi)
x=2π3,4π3\therefore x=\cfrac{2\pi}{3},\cfrac{4\pi}{3}
n=2\therefore n=2

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