I am currently studying for a first-year Math exam and am working through past exam questions. This one, however, has me totally perplexed (it's to do with planes and vectors and what-not):
A coordinate system is positioned so that the x-axis points North, the y-axis points West and the z-axis points vertically up. A man 2 meters high stands at the origin. The ground is sloping and has the equation x-y+4z = 0. How long is the man's shadow when the sun is due North at an elevation of 45 degrees?