9.4.16 Curvilinear integrals

Problem: Calculate the line integral of the \( 1^{\text {st }} \) kind: a) \( \int_{L}(x+y) d l \), where \( L: A B C \), b) \( \int_{L} x y d l \), where \( L:\left\{\begin{array}{c}\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1 \\ x \geq 0, \quad y \geq 0\end{array}\right. \).