![a_n=\sqrt{\dfrac{(2n-1)!}{(2n+1)!}}](https://tex.z-dn.net/?f=a_n%3D%5Csqrt%7B%5Cdfrac%7B%282n-1%29%21%7D%7B%282n%2B1%29%21%7D%7D)
Notice that
![\dfrac{(2n-1)!}{(2n+1)!}=\dfrac{(2n-1)!}{(2n+1)(2n)(2n-1)!}=\dfrac1{2n(2n+1)}](https://tex.z-dn.net/?f=%5Cdfrac%7B%282n-1%29%21%7D%7B%282n%2B1%29%21%7D%3D%5Cdfrac%7B%282n-1%29%21%7D%7B%282n%2B1%29%282n%29%282n-1%29%21%7D%3D%5Cdfrac1%7B2n%282n%2B1%29%7D)
So as
![n\to\infty](https://tex.z-dn.net/?f=n%5Cto%5Cinfty)
you have
![a_n\to0](https://tex.z-dn.net/?f=a_n%5Cto0)
. Clearly
![a_n](https://tex.z-dn.net/?f=a_n)
must converge.
The second sequence requires a bit more work.
![\begin{cases}a_1=\sqrt2\\a_n=\sqrt{2a_{n-1}}&\text{for }n\ge2\end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7Da_1%3D%5Csqrt2%5C%5Ca_n%3D%5Csqrt%7B2a_%7Bn-1%7D%7D%26%5Ctext%7Bfor%20%7Dn%5Cge2%5Cend%7Bcases%7D)
The monotone convergence theorem will help here; if we can show that the sequence is monotonic and bounded, then
![a_n](https://tex.z-dn.net/?f=a_n)
will converge.
Monotonicity is often easier to establish IMO. You can do so by induction. When
![n=2](https://tex.z-dn.net/?f=n%3D2)
, you have
![a_2=\sqrt{2a_1}=\sqrt{2\sqrt2}=2^{3/4}>2^{1/2}=a_1](https://tex.z-dn.net/?f=a_2%3D%5Csqrt%7B2a_1%7D%3D%5Csqrt%7B2%5Csqrt2%7D%3D2%5E%7B3%2F4%7D%3E2%5E%7B1%2F2%7D%3Da_1)
Assume
![a_k\ge a_{k-1}](https://tex.z-dn.net/?f=a_k%5Cge%20a_%7Bk-1%7D)
, i.e. that
![a_k=\sqrt{2a_{k-1}}\ge a_{k-1}](https://tex.z-dn.net/?f=a_k%3D%5Csqrt%7B2a_%7Bk-1%7D%7D%5Cge%20a_%7Bk-1%7D)
. Then for
![n=k+1](https://tex.z-dn.net/?f=n%3Dk%2B1)
, you have
![a_{k+1}=\sqrt{2a_k}=\sqrt{2\sqrt{2a_{k-1}}\ge\sqrt{2a_{k-1}}=a_k](https://tex.z-dn.net/?f=a_%7Bk%2B1%7D%3D%5Csqrt%7B2a_k%7D%3D%5Csqrt%7B2%5Csqrt%7B2a_%7Bk-1%7D%7D%5Cge%5Csqrt%7B2a_%7Bk-1%7D%7D%3Da_k)
which suggests that for all
![n](https://tex.z-dn.net/?f=n)
, you have
![a_n\ge a_{n-1}](https://tex.z-dn.net/?f=a_n%5Cge%20a_%7Bn-1%7D)
, so the sequence is increasing monotonically.
Next, based on the fact that both
![a_1=\sqrt2=2^{1/2}](https://tex.z-dn.net/?f=a_1%3D%5Csqrt2%3D2%5E%7B1%2F2%7D)
and
![a_2=2^{3/4}](https://tex.z-dn.net/?f=a_2%3D2%5E%7B3%2F4%7D)
, a reasonable guess for an upper bound may be 2. Let's convince ourselves that this is the case first by example, then by proof.
We have
![a_3=\sqrt{2\times2^{3/4}}=\sqrt{2^{7/4}}=2^{7/8}](https://tex.z-dn.net/?f=a_3%3D%5Csqrt%7B2%5Ctimes2%5E%7B3%2F4%7D%7D%3D%5Csqrt%7B2%5E%7B7%2F4%7D%7D%3D2%5E%7B7%2F8%7D)
![a_4=\sqrt{2\times2^{7/8}}=\sqrt{2^{15/8}}=2^{15/16}](https://tex.z-dn.net/?f=a_4%3D%5Csqrt%7B2%5Ctimes2%5E%7B7%2F8%7D%7D%3D%5Csqrt%7B2%5E%7B15%2F8%7D%7D%3D2%5E%7B15%2F16%7D)
and so on. We're getting an inkling that the explicit closed form for the sequence may be
![a_n=2^{(2^n-1)/2^n}](https://tex.z-dn.net/?f=a_n%3D2%5E%7B%282%5En-1%29%2F2%5En%7D)
, but that's not what's asked for here. At any rate, it appears reasonable that the exponent will steadily approach 1. Let's prove this.
Clearly,
![a_1=2^{1/2}](https://tex.z-dn.net/?f=a_1%3D2%5E%7B1%2F2%7D%3C2)
. Let's assume this is the case for
![n=k](https://tex.z-dn.net/?f=n%3Dk)
, i.e. that
![a_k](https://tex.z-dn.net/?f=a_k%3C2)
. Now for
![n=k+1](https://tex.z-dn.net/?f=n%3Dk%2B1)
, we have
![a_{k+1}=\sqrt{2a_k}](https://tex.z-dn.net/?f=a_%7Bk%2B1%7D%3D%5Csqrt%7B2a_k%7D%3C%5Csqrt%7B2%5Ctimes2%7D%3D2)
and so by induction, it follows that
![a_n](https://tex.z-dn.net/?f=a_n%3C2)
for all
![n\ge1](https://tex.z-dn.net/?f=n%5Cge1)
.
Therefore the second sequence must also converge (to 2).
6 hamsters, 3 cats, and 1 bird = 38 legs.
6H + 3C + 1B = 30
H = 4 C = 4 B = 2
6*4 + 3*4 + 1*2 = 38
Hope this helped :)
4 and 8 are corresponding angles. Corresponding angles are on the same side of parallel lines cut by a transversal
Search up Algebra Calculator on google and click the first website, it will help a lot and you won’t have to use points