Why doesn't mathematica evaluate this?

• To: mathgroup at smc.vnet.net
• Subject: [mg119818] Why doesn't mathematica evaluate this?
• From: Jacare Omoplata <walkeystalkey at gmail.com>
• Date: Fri, 24 Jun 2011 07:44:44 -0400 (EDT)

```Here's the output. Out[102] lists the assumptions I've used. It
doesn't evaluate out[104], but the inequality from Out[104] can be
arrived at by the inequalities In[105] and In[106], each of which
evaluate to true by themselves.

If the L.H.S. of In[105] is multiplied by the L.H.S. In[106], and the
R.H.S. of In[105] is multiplied by the R.H.S. of In[106], then the
inequality at Out[104] can be arrived at.

Is there a workaround?

-------------------------------------
output----------------------------------------------

In[102]:= \$Assumptions

Out[102]= {(x1 | x2 | t1 | t2 | u | c) \[Element] Reals, u < c, t1 <
t2, u > 0, x2 > x1, c t1 + x2 < c t2 + x1}

In[103]:= dT

Out[103]= -((t1 - (u x1)/c^2)/Sqrt[1 - u^2/c^2]) + ( t2 - (u x2)/c^2)/
Sqrt[1 - u^2/c^2]

In[104]:= FullSimplify[dT > 0]

Out[104]= c^2 t2 + u x1 > c^2 t1 + u x2

In[105]:= FullSimplify[(u/c) < 1]

Out[105]= True

In[106]:= FullSimplify[((x2 - x1)/(c*(t2 - t1))) < 1]

Out[106]= True

```

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