Q28 / 71 · NTA Abhyas (JEE Main) 2020 · Mathematics · Inverse Trigonometric Functions

If the function f:R→A defined as fx=tan-1⁡2x31+x6 is a surjective function, then the set A is equal to

  • A
    –π2,π2
  • Correct answer
    B
    –π4,π4
  • C
    –π2,π2
  • D
    0,π4

Solution

Let, x3=t∈R
Let, y=2t1+t2

⇒yt2-2t+y=0
∵t∈R, hence D≥0
⇒-22-4y2≥0⇒y∈-1,1
tan-1⁡y∈tan-1⁡-1,tan-1⁡1

Hence, the range of fx∈-π4,π4≡A

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

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