diff --git a/Ilia Smirnov_Heat equation_A.rtf b/Ilia Smirnov_Heat equation_A.rtf
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+{\rtf1\ansi\ansicpg1252\cocoartf2709
+\cocoatextscaling0\cocoaplatform0{\fonttbl\f0\fswiss\fcharset0 Helvetica;}
+{\colortbl;\red255\green255\blue255;}
+{\*\expandedcolortbl;;}
+\paperw11900\paperh16840\margl1440\margr1440\vieww11520\viewh8400\viewkind0
+\pard\tx566\tx1133\tx1700\tx2267\tx2834\tx3401\tx3968\tx4535\tx5102\tx5669\tx6236\tx6803\pardirnatural\partightenfactor0
+
+\f0\fs24 \cf0 u(0)=0; u(1)=1;\
+\
+1) Heat equation in 1D: \
+f(x)=-\uc0\u8706 (\u955 (x)\u8706 u/\u8706 x)/\u8706 x\
+\
+\pard\tx566\tx1133\tx1700\tx2267\tx2834\tx3401\tx3968\tx4535\tx5102\tx5669\tx6236\tx6803\pardirnatural\partightenfactor0
+\cf0 2) f(x)=const=h; \uc0\u955 (x)=const=\u955 ;\
+\
+3) h= -\uc0\u955 *(\u8706 u^2)/\u8706 x^2\
+\
+4) The second derivative: h= -\uc0\u955 u\'94(x); \
+\pard\tx566\tx1133\tx1700\tx2267\tx2834\tx3401\tx3968\tx4535\tx5102\tx5669\tx6236\tx6803\pardirnatural\partightenfactor0
+\cf0 \
+}
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