The south current (1.2 mph) is less than the rowing speed (2 mph), therefore any angle that compensates for the southward current will allow for steady progress across the stream without going downstream. The angle that exactly compensates for the southward current leaves an eastward vector, ensuring that one rows across the stream exactly eastward (so long as one is able to exactly maintain the angle and the 2 mph and the current remains at exactly 1.2 mph).

We therefore have a triangle whose hypotenuse is 2 mph, one side is 1.2 mph and we wish to solve for the angle opposite the 1.2 mph side.

Call the angle 'A' and we have:

sin(A) = 1.2/2.

A = asin(1.2/2) = 36.86 degrees

one should row at approximately 37 degrees