Integral - Length of the arc

[provasanteriores]

Let r be a positive constant. Consider the cylinder \(x^2 + y^2 \leq r^2\), and let C be the part of the cylinder that satisfies
\(0 \leq z \leq y .\)


Let a be the length of the arc along the base circle of C from the point (r,0,0) to the point \(( rcos \theta, rsin \theta, 0) 0 \leq \theta \leq \pi .\)
Let b be the length of the line segment from the point \(( rcos \theta, rsin \theta, 0) to the point (rcos \theta, rsin \theta, rsin \theta).\)Express a and b in terms of r, \theta. .

[provasanteriores]

Alguém para me ajudar?