Why isn't the first expression True ... ?
In[1]:= Log[a b] == Log[a] + Log[b] Out[1]= Log[a b] == Log[a] + Log[b] In[2]:= a = 10; b = 100; In[3]:= Log[a b] == Log[a] + Log[b] Out[3]= True
What am I missing? Is this a Type problem? Is there a Type for which the identity is not True?
Only true for positive a,b. If a<0 and b<0 then a b > 0 and the left side evaluates.
Reduce[Log[a b] == Log[a] + Log[b], {a, b}, Reals]
shows the condition
