2019/12/26
2019/11/30
coffee break 31
In autumn sales, I bought the 3D games.
Devil may cry 5
Division 2
Destiny 2 forsaken (dlc)
Now I am playing Assassin's creed Odyssey.
It is very open、wide and cool game which I am in 130hours over.
However, it will end soon.
If I immerse myself in one game, more games will be added, though.
Devil may cry 5
Division 2
Destiny 2 forsaken (dlc)
Now I am playing Assassin's creed Odyssey.
It is very open、wide and cool game which I am in 130hours over.
However, it will end soon.
If I immerse myself in one game, more games will be added, though.
2019/10/28
coffee break 30 (memory error)
I had a plan to assemble a new PC with a repaired motherboard.
I purchased new cpu and memories, and use other old parts.
The assembly was easy, but the bios doesn't start up when the power is turned on.
Testing any cases, I found out that one 8gb memory kit was bad,
so I sent the memory set to the shop.
Actually, the shop also found the error of the memory. and returned a replacement.
However, the same symptom occures again. why???
memories:G.Skill F4-3600C19D-8G*2
I purchased new cpu and memories, and use other old parts.
The assembly was easy, but the bios doesn't start up when the power is turned on.
Testing any cases, I found out that one 8gb memory kit was bad,
so I sent the memory set to the shop.
Actually, the shop also found the error of the memory. and returned a replacement.
However, the same symptom occures again. why???
memories:G.Skill F4-3600C19D-8G*2
2019/09/30
coffee break 29
I got the repaired MB asrock x470 Taichi from the shop.
The detail of the repair was a ROM exchange.
I already bought a new MB asus rog strix C7H,
so I have to think about how to handle it.
I would like to renew the second PC (win8.1).
However, I have to buy a CPU (Ryzen) and memories(DDR4) !!
The detail of the repair was a ROM exchange.
I already bought a new MB asus rog strix C7H,
so I have to think about how to handle it.
I would like to renew the second PC (win8.1).
However, I have to buy a CPU (Ryzen) and memories(DDR4) !!
2019/08/31
2019/07/25
coffee break 27 ( "celeste" )
I played "celeste" and saw the view of the summit of "celeste" mountain.
played time : 20hours
number of death : 5600
gotten strawberries : 20 pics
"celeste" is one of most difficult and hard games which I have played,
and I was not good at action games.
This game is very cool ,though.
played time : 20hours
number of death : 5600
gotten strawberries : 20 pics
"celeste" is one of most difficult and hard games which I have played,
and I was not good at action games.
This game is very cool ,though.
2019/06/26
coffee break 26 (my PC 5)
Finally, June 01, I requested for the shop to repair my motherboard,
which had an issue of sound .
I have done many things.
-drivers update
-Bios update
-change the jack and new cable of headphone
-OS update and changing the setting
-using USB-dac
and so on.
However, problems did not go away.
As nothing replies from the shop over three weeks,
I think the problems were replicated and the motherboard was going into repair.
Everything comes to him who waits.
Is it true?
which had an issue of sound .
I have done many things.
-drivers update
-Bios update
-change the jack and new cable of headphone
-OS update and changing the setting
-using USB-dac
and so on.
However, problems did not go away.
As nothing replies from the shop over three weeks,
I think the problems were replicated and the motherboard was going into repair.
Everything comes to him who waits.
Is it true?
2019/05/30
coffee break 25 (The Death)
"Negawaku wa Hana no moto nite Haru sinamu
sono Kisaragi no Mochizuki no koro"
----- Saigyo
2019/04/09 The man suddenly died.
2019/04/30
coffee break 24 (Heisei)
Today is end of Heisei.
Tomorrow, 2019,05.01, Reiwa is starting.
I have no feeling a little.
One day, one day goes on.
Tomorrow, 2019,05.01, Reiwa is starting.
I have no feeling a little.
One day, one day goes on.
2019/03/31
coffee break 23 (my PC 4)
Recently, the condition of the PC is not good.
Useing for about 30 minutes, the sound is cut off and can not be heard.
At the same time, an error "kp41" was also generated.
That could be counteracted by removing the usb device.
However, I still do not know the cause of the sound loss.
(1) driver (realtek HD audio)
(2) motherboard hardware error
(3) win10 (upgrade patches)
????
2019/02/28
a formula for π 4 ( arctan )
The inverse function of $\tan x$ is called $\arctan x$ .
That is, if $\tan \theta =x$ , then $\arctan x=\theta$ .
We have already gotten
\[ \int_{-\infty}^{\infty} \frac{1}{1+x^2}dx =\pi . \]
By some calculations. we will get
\[ \int_0^1 \frac{1}{1+x^2}dx = \frac{\pi}{4} . \]
In additions,
\[ \arctan y =\int_0^y \frac{1}{1+x^2}dx \]
Thus,
\[ \arctan y =\int_0^y (1-x^2+x^4-x^6+\cdots (-1)^nx^{2n})dx +R_n(y) \]
\[ \arctan y =y-\frac{y^3}{3}+\frac{y^5}{5}-\frac{y^7}{7}+\cdots+(-1)^n\frac{y^{2n+1}}{2n+1}+R_n(y) \]
As $R_n(y)\rightarrow 0$ ,
\[ \arctan y = y-\frac{y^3}{3}+\frac{y^5}{5}-\cdots \]
In this place, we put $y=1$ .
\[ \arctan 1 =\frac{\pi}{4}=1-\frac{1}{3}+\frac{1}{5}-\frac{1}{7}+\cdots \]
Therefore,
\[ \pi=4\left( \lim_{n\rightarrow \infty}\sum_{k=0}^n(-1)^k\frac{1}{2k+1} \right) \]
We got the series expression of $\pi$ .
That is, if $\tan \theta =x$ , then $\arctan x=\theta$ .
We have already gotten
\[ \int_{-\infty}^{\infty} \frac{1}{1+x^2}dx =\pi . \]
By some calculations. we will get
\[ \int_0^1 \frac{1}{1+x^2}dx = \frac{\pi}{4} . \]
In additions,
\[ \arctan y =\int_0^y \frac{1}{1+x^2}dx \]
Thus,
\[ \arctan y =\int_0^y (1-x^2+x^4-x^6+\cdots (-1)^nx^{2n})dx +R_n(y) \]
\[ \arctan y =y-\frac{y^3}{3}+\frac{y^5}{5}-\frac{y^7}{7}+\cdots+(-1)^n\frac{y^{2n+1}}{2n+1}+R_n(y) \]
As $R_n(y)\rightarrow 0$ ,
\[ \arctan y = y-\frac{y^3}{3}+\frac{y^5}{5}-\cdots \]
In this place, we put $y=1$ .
\[ \arctan 1 =\frac{\pi}{4}=1-\frac{1}{3}+\frac{1}{5}-\frac{1}{7}+\cdots \]
Therefore,
\[ \pi=4\left( \lim_{n\rightarrow \infty}\sum_{k=0}^n(-1)^k\frac{1}{2k+1} \right) \]
We got the series expression of $\pi$ .
2019/01/29
a formula for π 3
There are many equations of $\pi$ .
In first post of $\pi$ , we see
\[ \pi=\int_{-\infty}^{\infty}\frac{1}{1+x^2}dx \]
If we shorten the interval of integration from $(-\infty,\infty)$ to $[0,1]$ ,then
\[ \int_0^1\frac{1}{1+x^2}dx=\frac{\pi}{4} . \]
Because, put $x=\tan \theta$ . We know
\[ \frac{dx}{d\theta}=\frac{1}{\cos^2\theta} \]
and if $x=0$ , then $\theta=0$, and if $x\rightarrow 1$ , then $\theta\rightarrow \frac{\pi}{4}$ .
Therefore,
\[ \int_0^1\frac{1}{1+x^2}dx=\int_0^{\pi/4}\frac{1}{1+\tan^2\theta}\frac{1}{\cos^2\theta}d\theta=\frac{\pi}{4} . \]
We will get easily
\[ \int_{-1}^1\frac{1}{1+x^2}dx=\frac{\pi}{2} . \]
Thus,
\[ \int_1^{\infty}\frac{1}{1+x^2}dx=\int_{-\infty}^{-1}\frac{1}{1+x^2}dx=\frac{\pi}{4} . \]
In first post of $\pi$ , we see
\[ \pi=\int_{-\infty}^{\infty}\frac{1}{1+x^2}dx \]
If we shorten the interval of integration from $(-\infty,\infty)$ to $[0,1]$ ,then
\[ \int_0^1\frac{1}{1+x^2}dx=\frac{\pi}{4} . \]
Because, put $x=\tan \theta$ . We know
\[ \frac{dx}{d\theta}=\frac{1}{\cos^2\theta} \]
and if $x=0$ , then $\theta=0$, and if $x\rightarrow 1$ , then $\theta\rightarrow \frac{\pi}{4}$ .
Therefore,
\[ \int_0^1\frac{1}{1+x^2}dx=\int_0^{\pi/4}\frac{1}{1+\tan^2\theta}\frac{1}{\cos^2\theta}d\theta=\frac{\pi}{4} . \]
We will get easily
\[ \int_{-1}^1\frac{1}{1+x^2}dx=\frac{\pi}{2} . \]
Thus,
\[ \int_1^{\infty}\frac{1}{1+x^2}dx=\int_{-\infty}^{-1}\frac{1}{1+x^2}dx=\frac{\pi}{4} . \]