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Class 12 Inverse Trigonometric Functions · Long Answer3 Marksinverse_trigonometric_identities

Class 12 Maths · Inverse Trigonometric Functions · Long Answer #98

Prove \(\sec^2(\tan^{-1}2)+\operatorname{cosec}^2(\cot^{-1}5)=31\).

✅ Step-by-Step Solution

Final Answer: 31
  1. Let α=arctan2 and β=arccot5. Then tan α=2 and cot β=5.
  2. Using sec²α=1+tan²α gives sec²α=1+4=5.
  3. Using cosec²β=1+cot²β gives cosec²β=1+25=26.
  4. The sum is 5+26=31, as required.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Let α=arctan2 and β=arccot5. Then tan α=2 and cot β=5.
  • [1 mark] Using sec²α=1+tan²α gives sec²α=1+4=5.
  • [1 mark] Using cosec²β=1+cot²β gives cosec²β=1+25=26.
  • [0.5 marks] The sum is 5+26=31, as required.

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