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Chapter – 3 Concurrent forces in 3D
projecting vector A on the coordinate axes.
From equation (3.6), a vector A = Ax i + Ay j + Az k having a
magnitude A can be written as
A = A( cos i + cos j + cos k) (3.7)
3.2 Position Vector
As defined in chapter two, the position vector in 3D is
defined as a fixed vector which locates a point in space relative
to another point. Let us begin with the special case that is if r
extends from the origin of coordinates, O(0, 0, 0), to a point
P(x, y, z), as shown in Figure (3.7), then r can be expressed in
Cartesian vector form as
→ (3.8)
r =OP = x i + y j + z k
Fig. 3.7 Cartesian components of the position vector relative to the origin.
Consider the more general case, the position vector may be
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