AJ L. answered 04/18/23
Patient and knowledgeable Calculus Tutor committed to student mastery
This is simply just ∫02 3sec(πx/6)dx.
It is known that ∫sec(x)dx = ln(|sec(x)+tan(x)|) + C, so:
∫02 3sec(πx/6)dx
u = πx/6, du = (π/6)dx --> (18/π)du = 3dx
Converting our x-bounds to u-bounds, these are u= π(0)/6=0 to u=2π/6=π/3
(18/π)∫0π/3 sec(u)du
= (18/π)ln(|sec(u)+tan(u)|) [0,π/3]
= (18/π)ln(|sec(π/3)+tan(π/3)|) - (18/π)ln(|sec(0)+tan(0)|)
= (18/π)ln(2+√3) - (18/π)ln(1)
= (18/π)ln(2+√3) - (18/π)(0)
= (18/π)ln(2+√3)
≈ 7.546 (cubic units)
Hope this helped!