Can I get some good refs/resources of point-set topology... or something broader...
what I wanted to know -->
we define
**Boundary point**: Let $u \subset \mathbb{R}^n$, $x\in \mathbb{R}^n$ and $\forall r>0$, $B_r(x)\cap u \neq \phi$ and $B_n(x) \cap u^c \neq \phi$, then we say $x$ is a boundary point.
Here, is the set $u$ a region?...like continuous and connected etc....(words not to be taken with mathematical rigour)...
say I define some scattered points in $u$...then how do I define a boundary and an interior
what I wanted to know -->
we define
**Boundary point**: Let $u \subset \mathbb{R}^n$, $x\in \mathbb{R}^n$ and $\forall r>0$, $B_r(x)\cap u \neq \phi$ and $B_n(x) \cap u^c \neq \phi$, then we say $x$ is a boundary point.
Here, is the set $u$ a region?...like continuous and connected etc....(words not to be taken with mathematical rigour)...
say I define some scattered points in $u$...then how do I define a boundary and an interior
We define a reverse chain complex $X_{\bullet}$ of $A$-modules and $A$-module homomorphisms $d_{i} : X_i \to X_{i-1}$ to be a usual chain complex of $A$-modules except the condition $\operatorname{im} d_i \subset \ker d_{i-1}$ gets reversed, that is: $\ker d_{i-1} \subset \operatorname{im} d_i$.
...
