@DeanMiller: I think it helps, but it is a bit confusing as the OP uses a definition of approximate spectrum that differs from Wikipedia's but which according to the addendum of the accepted answer is equivalent. However, this is not the definition used in the main part of the answer! Moreover, they don't show the equivalence but only the implication in one direction.
4 I am studying geometric measure theory, and I am having some trouble understanding how to deal with approximate tangent spaces. I would like an example/exhibition of an approximate tangent space in a regular setting (so that it does coincide with a classic vector subspace). First of all, the definition.
A protractor is used to draw and measure angles. An angle is the amount of turn between two lines. Angles are measured in degrees with the symbol °. Angles can be labelled with 3 letters (eg DEF) to ...
An angle is created when two lines meet. There are different types of angles based on their measurement. Let's look at the different types. A right angle looks like the corner of a square or the edge ...