School of Mathematics and Statistics, The University of Sydney
 12. Lines in space
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The parametric scalar equations

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Suppose that the point P0 has coordinates x0,y0,z0, and the non-zero vector v has components a,b,c.

Let x,y,z be the coordinates of an arbitrary point P on the line l.

Then

v = ai + bj + ck

and the position vectors of P0 and P are given by

----> OP0 =  r0 = x0i + y0j + z0k

and

---> OP  = r = xi + yj + zk

respectively. The parametric vector equation may be rewritten as

(x - x0)i + (y-  y0)j + (z - z0)k = t(ai + bj + ck),

that is,

x - x0 =  ta,  y-  y =  tb,       0  z-  z0 = tc,

with t  (- R. These equations are called parametric scalar equations of the line.

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