[see also: issue, subject, topic, problem, point] This proves one half of (2); the other half is a matter of direct computation.
The first of the above equalities is a matter of definition, and the second follows from (3).
It is a simple matter <a routine matter/a matter of routine> to show that......
It is an easy matter to use Theorem 10 to construct all manner of interesting Peano continua [= continua of different kinds]
We conclude that, no matter what the class of b is, we have an upper bound on M.
Nevertheless, no matter how small a neighbourhood of x we take, the image will be......
[see also: important, relevant] It does not matter in the least whether......
Whether or not this is correct does not matter; we are trying to motivate the proof that follows.