Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 19H Solution Created 2026-09-24 Updated 2026-10-14
With the uniform prior, the binomial likelihood gives the beta distribution posterior . Under squared-error loss, the Bayes estimator is the posterior mean:
The production manager's prior gives posterior density proportional to . Minimizing gives the weighted posterior meanusing the supplied beta function. Cross multiplication shows exactly when , so it is greater unless .
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 18D Solution Created 2026-09-24 Updated 2026-10-03
Let be the velocity potential. The linearized deep-water equations are for , and at , with zero normal velocity at the four side walls. The normal modes arewhere are not both zero. The free-surface conditions give the dispersion relation for a deep-water gravity wave:
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 17C Solution Created 2026-09-24 Updated 2026-10-03
Remove a small disc about and apply Green second identity to and . Since and , the shrinking inner boundary contributes and gives
For the unit disc, the method of images gives the Dirichlet Green functionwhich vanishes on the boundary by the hinted identity. The boundary representation with evaluates the normal derivative of at , giving the Poisson kernel
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 16B b Created 2026-09-24 Updated 2026-09-24
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Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 15G Solution Created 2026-09-24 Updated 2026-10-03
Differentiate the parametrized surface. The coefficients of the first fundamental form simplify toIf , then . MoreoverThus the second-fundamental-form coefficients satisfy and . The Gaussian curvature is consequently
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 14A b Created 2026-09-24 Updated 2026-09-24
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Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 12F b Created 2026-09-24 Updated 2026-09-24
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Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 11G c Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 11G b Created 2026-09-24 Updated 2026-09-24
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Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 4 10E Solution Created 2026-09-24 Updated 2026-10-03
A self-adjoint operator satisfies . If , then , so . An eigenvector exists over ; its orthogonal complement is -invariant. Induction on dimension produces an orthonormal basis of eigenvectors, proving the finite-dimensional spectral theorem.
A self-adjoint is positive definite exactly when every eigenvalue is positive, since in an eigenbasis. The quadratic forms of two positive-definite operators add, so their sum is positive definite.
The same eigenbasis shows that exactly when is positive definite for every and negative definite for every . Finally, if is a unit eigenvector of with eigenvalue , the Rayleigh quotient bounds giveThus every eigenvalue of lies in .
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 3 9H iii Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 3 9H ii Created 2026-09-24 Updated 2026-09-24
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Past exam of the mathematics course of the University of Cambridge 2018 ib Paper 3 8B Solution Created 2026-09-24 Updated 2026-10-14
A Hermitian operator satisfies on its operator domain. HereTwo integration by parts operations, together with the boundary conditions in the Hamiltonian domain, show that the kinetic term is Hermitian; multiplication by the real function is Hermitian as well. Thus is Hermitian.
For a time-independent operator , the Schrödinger equation and its adjoint give the Ehrenfest theoremUsing the canonical commutation relation ,Consequently
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