Question Detail
Question
By Wallis' formula, evaluate ∫₀^(π/2) cos⁹x dx
Correct Answer
Option C is the correct answer.
Detailed Explanation
By Wallis' formula for an odd power n=9: (8/9)(6/7)(4/5)(2/3)(1)=128/315.
Hint
For an odd power, multiply successive factors (n-1)/n down to 1, with no factor of π.