Wednesday, 28 June 2017

cardinals - Cardinality of infinite sequences of $0$ and $1$ $geq |mathbb{R}|$

Think of all infinite sequences of $0$s and $1$s. Let the set be $S$. I want to prove that the cardinality $|S|$ is greater than or equal to $|\mathbb{R}|$. I think it is useful to use the fact that the set $T$ of reals in $(0,1)$ has the same cardinality as $\mathbb{R}$. If I can create an injective function from $S$ to $T$ then it would imply $|S|=|T|=|\mathbb{R}|$. I think of taking the the infinite number in $S$, typically 10011001... and map to the number in $T$ with that decimal expansion, so 0.10011001.... Then wouldn't that be an injection?

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real analysis - How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$

How to find $\lim_{h\rightarrow 0}\frac{\sin(ha)}{h}$ without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...