Mark M. answered 12/02/24
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
sinx = x - x3/3! + x5/5! - x7/7! + ...
So, sinx / x = 1 - x2/3! + x4/5! - x6/7! + ...
Therefore, ∫ [sinx / x]dx = x - (1/3)(x3/3!) + (1/5)(x5/5!) -(1/7)(x7/7!) + ...
= ∑(n=1 to ∞) [(-1)n+1(1/((2n-1)(2n-1)!)x2n-1]
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3(2n+1)/(4n) = 3(2)(2n)/(4n) = 6(1/2)n
So, we have 6∑(n=0 to ∞) (1/2)n = 6[ 1 / (1 - 1/2)] = 12