English
If y lies in the target of the chart extChartAt I x, then writtenInExtChartAt I I x (chartAt H' x x) (chartAt H' x).symm y = y; compatibility with chartAt is preserved under composition.
Русский
Если y принадлежит цели extChartAt I x, то writtenInExtChartAt I I x (chartAt H' x x) (chartAt H' x).symm y = y; совместимость сохраняется при композиции.
LaTeX
$$$writtenInExtChartAt I I (chartAt H' x x) (chartAt H' x).symm y = y$ for $y$ in the target of extChartAt I x.$$
Lean4
theorem writtenInExtChartAt_chartAt_symm_comp [ChartedSpace H H'] (x : M') {y}
(hy :
y ∈
letI := ChartedSpace.comp H H' M';
(extChartAt I x).target) :
(letI := ChartedSpace.comp H H' M'
writtenInExtChartAt I I (chartAt H' x x) (chartAt H' x).symm y) =
y :=
by
letI := ChartedSpace.comp H H' M'
simp_all only [mfld_simps, chartAt_comp]