Q15 / 71 · NTA Abhyas (JEE Main) 2020 · Mathematics · Inverse Trigonometric Functions

If tan-112x+1+tan-114x+1=cot-1x22, then the number of all possible values of x is/are

  • A
    1
  • Correct answer
    B
    2
  • C
    3
  • D
    0

Solution

tan-112x+1+14x+11-12x+1⋅14x+1=tan-12x2
tan-16x+28x2+6x=tan-12x2
Therefore, 3x+14x2+3x=2x2
x23x+1=24x2+3x
3x3-7x2-6x=0
x3x2-7x-6=0
xx-33x+2=0
We take x=3,0 because when x=-23, LHS of the given equation will be negative whereas tan-12x2 is positive.
Hence, the number of values =2

Hence, the correct answer is option: 'B'.

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