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Three Dimensional Geometry

Question
CBSEENMA12033280

The cartesian equations of a line are 6 x – 2 = – 3 y + 1 = 2 z = 2. Find the direction ratios of the line and write down the vector equation of the line through (2, – 1, –1) which is parallel to the given line.

Solution
The equation of the line are 6 x – 2 = 3 y + 1 = 2 z – 2
or   6 space open parentheses straight x minus 1 third close parentheses space equals space 3 open parentheses straight y plus 1 third close parentheses space equals space 2 left parenthesis straight z minus 1 right parenthesis
or    fraction numerator straight x minus begin display style 1 third end style over denominator 1 end fraction space equals space fraction numerator straight y minus open parentheses negative begin display style 1 third end style close parentheses over denominator 2 end fraction space equals space fraction numerator straight z minus 1 over denominator 3 end fraction
∴     direction-ratios of the line are 1, 2, 3.
therefore              straight m with rightwards arrow on top space equals space straight i with hat on top space plus space 2 space straight j with hat on top space plus space 3 space straight k with hat on top
Required line passes through (2, – 1, – 1)
therefore space space space space straight a with rightwards arrow on top space equals space 2 space straight i with hat on top space minus space straight j with hat on top space minus space straight k with hat on top
Let  straight r with rightwards arrow on top be the position vector of any point on the line. 
∴      the vector equation of required line is
 straight r with rightwards arrow on top space equals space straight a with rightwards arrow on top space plus space straight lambda straight m with rightwards arrow on top space space space or space space space straight r with rightwards arrow on top space equals space left parenthesis 2 space straight i with hat on top space minus space straight j with hat on top space minus space straight k with hat on top right parenthesis space space plus space straight lambda space open parentheses straight i with hat on top space plus space 2 space straight j with hat on top space plus space 3 space straight k with hat on top close parentheses
where λ is a parameter.

Some More Questions From Three Dimensional Geometry Chapter

Find the direction cosines of x, y and z-axis.