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| | College Mathematics Journal, The: Predicting sunrise and sunset times (Site not responding. Last check: 2007-10-20) |
 | | We also note in Figure 1 that r is the length of the earth-sun vector [left angle bracket]x^sub s^, y^sub s^, z^sub s^[right angle bracket], [theta] is the angle between this vector and the positive x-axis, and r^sub p^ is the length of the projection [left angle bracket]x^sub s^, y^sub s^, 0[right angle bracket]. |
 | | Though the vector [left angle bracket]x^sub 0^, y^sub 0^, z^sub 0^[right angle bracket] was introduced as the location of our observer, it also can be thought of as a normal vector for the plane tangent to the earth's surface at the observer's location. |
 | | Note that angle M also is the angle in excess of 2[pi] radians that the earth must rotate in order for the sun to be directly overhead again. |
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