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NCERT Class 12 · Ch 6 Miscellaneous Exercise · Q14

NCERT Class 12 Maths · Chapter 6 Applications Of Derivatives · Miscellaneous Exercise Question 14

Find the height and volume of the maximum-volume cylinder inscribed in a sphere of radius R.
Optimal cylinder in a unit-sphere axial section
Optimal cylinder in a unit-sphere axial section

💡 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: h=2R/√3; Vmax=4πR³/(3√3).
  1. The axial section gives r²+(h/2)²=R², so V=πh(R²−h²/4), 0<h<2R.
  2. V′=π(R²−3h²/4), zero at h=2R/√3. It is positive before and negative after; endpoint volumes vanish.
  3. Then r²=2R²/3 and Vmax=π(2R²/3)(2R/√3)=4πR³/(3√3).

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