Paper 3, Section II, D

Asymptotic Methods
Part II, 2020

(a) Find the leading order term of the asymptotic expansion, as xx \rightarrow \infty, of the integral

I(x)=03πe(t+xcost)dtI(x)=\int_{0}^{3 \pi} e^{(t+x \cos t)} d t

(b) Find the first two leading nonzero terms of the asymptotic expansion, as xx \rightarrow \infty, of the integral

J(x)=0π(1cost)exln(1+t)dtJ(x)=\int_{0}^{\pi}(1-\cos t) e^{-x \ln (1+t)} d t