What complexity have a log(sum) shape?

[cym13 via Digitalmars-d]

On Tuesday, 8 December 2015 at 20:56:28 UTC, cym13 wrote:
> On Tuesday, 8 December 2015 at 17:33:49 UTC, Andrei 
> Alexandrescu wrote:
>> On 12/08/2015 12:12 PM, Timon Gehr wrote:
>>> O(log(n+m)) = O(log(n)+log(m)).
>>
>> Noice. Yes I did miss it. Thx!! -- Andrei
>
> Surely I'm missing something obvious but why is it true exactly?

Damn, I missed Timon's post, here is the link for anybody else: 
http://forum.dlang.org/thread/n3qq6e$2bis$1@digitalmars.com?page=10#post-n42ft2:2498u:241:40digitalmars.com