2. Recommended procedures and functions to use

• any needed from the page of suggested matrix procedures;

• one to multiply a vector by a matrix;

• one to turn latitude, longitude in radians into Cartesian coordinates:

• any others that are useful for clarity, e.g., one for degrees to radians.

Please use arrays for vectors and matrices, for example, p[], R[][], instead of using a different letter for each vector or matrix entry. This is usually better programming procedure, as it permits vector and matrix calculations to be done with loops rather than many separate statements. Then if there is a bug in the loop, it will be dramatic and will be more apt to be discovered than a bug in one of several separate statements. As mentioned, for clarity you can define x,y,z to be the indices 0,1,2.