JEE AdvancedHardQuestion 360011
Question
If y = tan⁻¹(2x/(1−x²)), then dy/dx for |x| < 1 is:
- A2/(1+x²)Correct
- B1/(1+x²)
- C2(1−x²)/(1+x²)²
- D1/(1+4x²)
Correct answer
2/(1+x²)
Explanation
Recognize: 2x/(1−x²) = tan(2θ) when x = tan θ. So y = tan⁻¹(tan 2θ) = 2θ = 2tan⁻¹x. dy/dx = 2/(1+x²).