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NCERT Class 12 · Ch 7 Exercise 7.6 · Q9

NCERT Class 12 Maths · Chapter 7 Integrals · Exercise 7.6 Question 9

Evaluate \(\int x \operatorname{acos}{\left(x \right)}\, dx\).

💡 Concept Hints

  1. Identify the domain and the inner and outer functions, or the relevant one-sided limits.
  2. Apply the appropriate differentiation or limit rule, keep all chain factors, and check exceptional points.

✅ Step-by-Step Solution

Final Answer: \(- \frac{x \sqrt{1 - x^{2}}}{4} + \frac{\left(2 x^{2} - 1\right) \operatorname{acos}{\left(x \right)}}{4}\) + C.
  1. Work on each open interval where the original integrand is real and defined.
  2. Choose u=\(\operatorname{acos}{\left(x \right)}\) and v=\(\frac{x^{2}}{2}\), so dv=\(x\)dx and du=\(- \frac{1}{\sqrt{1 - x^{2}}}\)dx.
  3. Apply ∫u dv=uv−∫v du. The remaining integrand v·u′ is \(- \frac{x^{2}}{2 \sqrt{1 - x^{2}}}\). Integrate it and subtract from uv.
  4. An antiderivative is F(x)=\(- \frac{x \sqrt{1 - x^{2}}}{4} + \frac{\left(2 x^{2} - 1\right) \operatorname{acos}{\left(x \right)}}{4}\).
  5. Differentiate this expression to check that F′(x)=\(x \operatorname{acos}{\left(x \right)}\). Add an arbitrary constant C on each domain component.

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