Another question which will no doubt result in all sorts of esoteric arguments.....
Simple Pythagoras suggests "39 degrees" (square root of 15 squared plus 36 squared), but
- Can a diagonal be measured in "degrees"?
- What about the curvature of the Earth - away from the equator the 36 degrees north will curve in a bit, so the hypoteneuse of the triangle won't be straight?
- If he starts near the poles, he could be affected by the old chestnut of walking right round the Earth, etc.
Without knowing the lat. and long. of the start point, it is impossible to say. In general, the answer is going to be greater if the starting point is in the S. hemisphere rather than in the N. hemisphere.