multivariate functions rename to multivariate space? Move elsewhere? Later h3 at least, in line integrals, metrics etc
more on trig to own h3 after integration tangent to there trig identities of integration there
mutlivar integral of scalar field to own h3, relies on metrics
After grad of vector. Show is conservative. Definition of conservative field, link to curl?
Helmholtz. All vector fields can be decomposed to one with div 0 and one with curl 0 Laplace equation Helmholtz equation Poissons equation
optimisation univariate has hessian - belongs in multivar
page on separation of variables to solve page on lie group method
Curl of any vector field has divergence 0