Objective: 
To find the magnetic flux density at a point due
to a current flowing in an infinitely long wire. This is useful
because it gives us a simple equation to use on the next page
where we determine Ampère's Law. Ampère's Law is
required to find the boundary conditions for magnetic fields. 
Steps: 

To find the total effect of the current at a point
we need to find equations which will simplify the calculation.
The most useful are the perpendicular distance between the wire
and the point (a constant) and a relationship between the length
of an element and the angle it makes with the point. 



Combining the equations produces an integral with
a simple solution. 