http://mathcs.chapman.edu/webwork2_f...38556e3171.png and http://mathcs.chapman.edu/webwork2_f...37768eabf1.png, find a unit vector with positive first coordinate orthogonal to both http://mathcs.chapman.edu/webwork2_f...6067c94d71.png and http://mathcs.chapman.edu/webwork2_f...1571a542a1.png.

I can do the calculation myself, i'm just not sure where to start