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Class 12 Inverse Trigonometric Functions · Short Answer2 Marksbranch_sensitive_simplification

Class 12 Maths · Inverse Trigonometric Functions · Short Answer #91

For a>0 and |x|<a, simplify \(\tan^{-1}[x/\sqrt{a^2-x^2}]\).

✅ Step-by-Step Solution

Final Answer: sin⁻¹(x/a)
  1. Let θ=arcsin(x/a). Since |x|<a and a>0, θ∈(−π/2,π/2).
  2. Its cosine is √(a²−x²)/a>0; hence tan θ=(x/a)/(√(a²−x²)/a)=x/√(a²−x²).
  3. Taking the principal arctangent gives θ=arcsin(x/a).

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Let θ=arcsin(x/a). Since |x|<a and a>0, θ∈(−π/2,π/2).
  • [1 mark] Its cosine is √(a²−x²)/a>0; hence tan θ=(x/a)/(√(a²−x²)/a)=x/√(a²−x²).
  • [0.5 marks] Taking the principal arctangent gives θ=arcsin(x/a).

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