What is this direction cosine for the vector (7,4,-3) with the positive z-axis?
a) -3/74
b) -3/√(74)
c) 3/74
d) 3/√(74)
The directional cosine is
-3 / sqrt [ 7^2 + 4^2 + (-3)^2 ] =
-3 / sqrt [ 49 + 16 + 9 ] =
-3 / sqrt [ 74 ]
+956 
