RE: Question about precision.
- To: mathgroup at smc.vnet.net
- Subject: [mg38421] RE: [mg38405] Question about precision.
- From: "David Park" <djmp at earthlink.net>
- Date: Sat, 14 Dec 2002 03:20:15 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Web-Feng, For machine precision numbers, the default, Mathematica normally only displays 6 places of precision even though it calculates to full machine precision - 16 places. To show more places use NumberForm. Sqrt[1.3] NumberForm[%, 16] 1.14018 1.140175425099138 You can use the Option Inspector to change the number of places normally displayed. (Also N is only used to convert exact numbers to approximate numbers and affects the display ONLY if you specify more than machine precision. So NumberForm, and not N, is the correct function to control the display.) David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Wen-Feng Hsiao [mailto:wfhsiao at libra.seed.net.tw] To: mathgroup at smc.vnet.net Dear experts, I try to find the square root of 1.3, but obtain an not so correct answer. Could someone point me how to do? My trials are the followings. In[28]:= Sqrt[1.3] Out[28]= 1.14018 In[29]:= Precision[Sqrt[1.3]] Out[29]= 16 In[30]:= N[Sqrt[1.3], 50] Out[30]= 1.14018 In[31]:= 1.14018*1.14018 Out[31]= 1.30001 The more precise answer should be In[32]:= 1.140175425*1.140175425 Out[32]= 1.3 Thanks for your help! Wen-Feng Hsiao