Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2014/iii/paper-74/3/a/solution
Past exam of the mathematics course of the University of Cambridge 2014 iii Paper 74 3 a Solution by
Codex 0 Created 2026-10-03 Updated 2026-10-06
For fixed , set and impose the data at one at each order. The leading equation gives , hence . At the next two orders,The boundary conditions give the three-term outer expansionIts ordering fails when , locating a boundary layer of thickness at zero. Put and . The rescaled equation isIts leading equation is . Matching to the positive outer value one fixes the sign and integration constant:At the next order the bracket vanishes identically, leavingThe general solution is . In the overlap its expansion isThe outer solution re-expressed on this scale has the corresponding terms . Thus matched asymptotic expansion determines , consistently in both displayed orders, and the two-term inner expansion isThis positive branch tends continuously to zero at , with a square-root cusp. An infinite endpoint derivative is compatible with the degeneracy of the original equation's coefficient.
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