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Class 12 Inverse Trigonometric Functions · Long Answer3 Marksinverse_trigonometric_identities

Class 12 Maths · Inverse Trigonometric Functions · Long Answer #93

Prove \(\cos[\sin^{-1}(3/5)+\cot^{-1}(3/2)]=6/(5\sqrt{13})\).

✅ Step-by-Step Solution

Final Answer: Identity proved.
  1. Let α=arcsin(3/5) and β=arccot(3/2), both acute.
  2. The ratios are sin α=3/5, cos α=4/5, sin β=2/√13 and cos β=3/√13.
  3. The addition formula gives cos(α+β)=(4·3−3·2)/(5√13).
  4. The value is 6/(5√13), as required.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Let α=arcsin(3/5) and β=arccot(3/2), both acute.
  • [1 mark] The ratios are sin α=3/5, cos α=4/5, sin β=2/√13 and cos β=3/√13.
  • [1 mark] The addition formula gives cos(α+β)=(4·3−3·2)/(5√13).
  • [0.5 marks] The value is 6/(5√13), as required.

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