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VMWare Player:The default sound device cannot be opened:

如果VMWare player啟動linux時出現:
The default sound device cannot be opened: A device ID has been used that is out of range for your system. Sound will be disconnected

 這個可能是使用"瑞昱高傳真音效"卡,設定上的問題,
 我把"音效裝置連接設定",改成"AC97前置面板"(原本是HD Audio前置面板)
 就可以在VMWare Player下的Fedora 20聽到聲音了。

 或者參考以下的改法:
https://communities.vmware.com/thread/406063
If you have RealTek speakers, look within the RealTek HD Audio Manager.  Select the yellow folder near the analog panel, and make sure "Disable front panel jack detection" is selected.  This fixed the problem for me.

Apparently RealTeks detection blocks the linux virtual machine from accessing the resource, and causes the error.

直角三角形一定有一邊長是無理數,要不然有一角度是無理數

高中時,猜想的:
直角三角形一定有一邊長是無理數,要不然必有一角度是無理數。

我不會證,但由泰勒展開式,似乎可推得此結果。
不曉得是不是這樣?有沒有人證過?