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NCERT Class 12 · Ch 2 Miscellaneous Exercise · Q8

NCERT Class 12 Maths · Chapter 2 Inverse Trigonometric Functions · Miscellaneous Exercise Question 8

Prove tan⁻¹√x=(1/2)cos⁻¹((1−x)/(1+x)), 0≤x≤1.

💡 Concept Hints

  1. Recall the principal range of the inverse function before simplifying.
  2. Find an angle with the required trigonometric value, then verify it belongs to the principal range.

✅ Step-by-Step Solution

Final Answer: The identity holds.
  1. Set θ=tan⁻¹√x∈[0,π/4].
  2. cos 2θ=(1−tan²θ)/(1+tan²θ)=(1−x)/(1+x).
  3. Since 2θ∈[0,π/2]⊂[0,π], cos⁻¹((1−x)/(1+x))=2θ. Divide by 2.

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