Q.

If cotθ=3x-112x, then cscθ-cotθ is equal to ?


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a

6x

b

-16x

c

16x or -6x

d

6or -16x  

answer is C.

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Detailed Solution

Given that, cotθ=3x-112x.
We know the trigonometric identity,
csc2θ-cot2θ=1  csc2θ=1+cot2θ Substituting the given value cotθ=3x-112x in the above equation, we get
 csc2θ=1+(3x-112x)2  csc2θ=1+9x2+1144x2-12  csc2θ=9x2+1144x2+12  csc2θ=(3x+112x)2  cscθ=±(3x+112x) If cscθ=3x+112x,
then cscθ-cotθ
=3x+112x-(3x-112x)
 =16x If cscθ=-(3x+112x)=-3x-112x,
then cscθ-cotθ
=-3x-112x-(3x-112x)  =-6x Therefore, cscθ-cotθ=-6or  16x.
Hence, the correct option is (3).
 
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