Revert "More typos"

This reverts commit 7f657dd22ac20d22698c53b23f0057e1a12c09b7.
Revert "Revert "More typos""

This reverts commit 33e2f56acaec0faa8c1c860b8ea08e485c7652b2.
Revert "Revert "Revert "More typos"""

This reverts commit 4d10ea979274cc257f04c91faf53c2c4b40445c5.
Functions to cache matrix inverse