How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$
$begingroup$
How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$ without lhopital rule?
I know when I use lhopital I easy get
$$ lim_{hrightarrow 0}frac{cos(ah)a}{1} = a$$ but I don't know how to behave without that way
real-analysis limits limits-without-lhopital
$endgroup$
add a comment |
$begingroup$
How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$ without lhopital rule?
I know when I use lhopital I easy get
$$ lim_{hrightarrow 0}frac{cos(ah)a}{1} = a$$ but I don't know how to behave without that way
real-analysis limits limits-without-lhopital
$endgroup$
add a comment |
$begingroup$
How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$ without lhopital rule?
I know when I use lhopital I easy get
$$ lim_{hrightarrow 0}frac{cos(ah)a}{1} = a$$ but I don't know how to behave without that way
real-analysis limits limits-without-lhopital
$endgroup$
How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$ without lhopital rule?
I know when I use lhopital I easy get
$$ lim_{hrightarrow 0}frac{cos(ah)a}{1} = a$$ but I don't know how to behave without that way
real-analysis limits limits-without-lhopital
real-analysis limits limits-without-lhopital
asked Jan 28 at 12:18
VirtualUserVirtualUser
1,120117
1,120117
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2 Answers
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votes
$begingroup$
Hint:
$$frac{sin(ha)}{h} = acdotfrac{sin(ha)}{ha}$$
Also, remember what $$lim_{xto 0}frac{sin(x)}{x}$$ is equal to?
$endgroup$
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
add a comment |
$begingroup$
Notice that $sin(x) = sum_{k = 0}^infty (-1)^k frac{x^{2k + 1}}{(2k + 1)!}$ for all $x in mathbb R$. Thus,
$$ frac{sin(ah)}{h} = frac 1 h sum_{k = 0}^infty (-1)^k frac{(ah)^{2k + 1}}{(2k + 1)!} = sum_{k = 0}^infty (-1)^k frac{a^{2k + 1} h^{2k}}{(2k + 1)!} longrightarrow a$$
as $h to 0$ by dominated convergence for example.
$endgroup$
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Hint:
$$frac{sin(ha)}{h} = acdotfrac{sin(ha)}{ha}$$
Also, remember what $$lim_{xto 0}frac{sin(x)}{x}$$ is equal to?
$endgroup$
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
add a comment |
$begingroup$
Hint:
$$frac{sin(ha)}{h} = acdotfrac{sin(ha)}{ha}$$
Also, remember what $$lim_{xto 0}frac{sin(x)}{x}$$ is equal to?
$endgroup$
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
add a comment |
$begingroup$
Hint:
$$frac{sin(ha)}{h} = acdotfrac{sin(ha)}{ha}$$
Also, remember what $$lim_{xto 0}frac{sin(x)}{x}$$ is equal to?
$endgroup$
Hint:
$$frac{sin(ha)}{h} = acdotfrac{sin(ha)}{ha}$$
Also, remember what $$lim_{xto 0}frac{sin(x)}{x}$$ is equal to?
answered Jan 28 at 12:19
5xum5xum
91.8k394161
91.8k394161
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
add a comment |
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
$begingroup$
Thanks for show that simple trick!
$endgroup$
– VirtualUser
Jan 28 at 12:45
add a comment |
$begingroup$
Notice that $sin(x) = sum_{k = 0}^infty (-1)^k frac{x^{2k + 1}}{(2k + 1)!}$ for all $x in mathbb R$. Thus,
$$ frac{sin(ah)}{h} = frac 1 h sum_{k = 0}^infty (-1)^k frac{(ah)^{2k + 1}}{(2k + 1)!} = sum_{k = 0}^infty (-1)^k frac{a^{2k + 1} h^{2k}}{(2k + 1)!} longrightarrow a$$
as $h to 0$ by dominated convergence for example.
$endgroup$
add a comment |
$begingroup$
Notice that $sin(x) = sum_{k = 0}^infty (-1)^k frac{x^{2k + 1}}{(2k + 1)!}$ for all $x in mathbb R$. Thus,
$$ frac{sin(ah)}{h} = frac 1 h sum_{k = 0}^infty (-1)^k frac{(ah)^{2k + 1}}{(2k + 1)!} = sum_{k = 0}^infty (-1)^k frac{a^{2k + 1} h^{2k}}{(2k + 1)!} longrightarrow a$$
as $h to 0$ by dominated convergence for example.
$endgroup$
add a comment |
$begingroup$
Notice that $sin(x) = sum_{k = 0}^infty (-1)^k frac{x^{2k + 1}}{(2k + 1)!}$ for all $x in mathbb R$. Thus,
$$ frac{sin(ah)}{h} = frac 1 h sum_{k = 0}^infty (-1)^k frac{(ah)^{2k + 1}}{(2k + 1)!} = sum_{k = 0}^infty (-1)^k frac{a^{2k + 1} h^{2k}}{(2k + 1)!} longrightarrow a$$
as $h to 0$ by dominated convergence for example.
$endgroup$
Notice that $sin(x) = sum_{k = 0}^infty (-1)^k frac{x^{2k + 1}}{(2k + 1)!}$ for all $x in mathbb R$. Thus,
$$ frac{sin(ah)}{h} = frac 1 h sum_{k = 0}^infty (-1)^k frac{(ah)^{2k + 1}}{(2k + 1)!} = sum_{k = 0}^infty (-1)^k frac{a^{2k + 1} h^{2k}}{(2k + 1)!} longrightarrow a$$
as $h to 0$ by dominated convergence for example.
answered Jan 28 at 12:32
YaddleYaddle
3,136829
3,136829
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