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Three Dimensional Geometry

Question
CBSEENMA12033262

Find the vector and Cartesian equations of the line through the point (5, 2, – 4) and which is parallel to the vector 3 straight i with overparenthesis on top space plus space 2 straight j with overparenthesis on top space minus space 8 space straight k with overparenthesis on top.

Solution
Since the line passes through the point (5, 2, 4) and is parallel to the vector 3 straight i with hat on top space plus space 2 straight j with hat on top space minus space 8 straight k with hat on top.
therefore space space space space straight a with rightwards arrow on top space equals space 5 straight i with hat on top space plus space 2 straight j with hat on top space minus space 4 straight k with hat on top comma space space space space straight m with rightwards arrow on top space equals space 3 straight i with hat on top space plus space 2 straight j with hat on top space minus space 8 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 line is
                            straight r with rightwards arrow on top space equals space straight a with rightwards arrow on top plus space straight lambda straight m with rightwards arrow on top
or                      straight r with rightwards arrow on top space equals space left parenthesis 5 space straight i with hat on top space plus space 2 space straight j with hat on top space minus space 4 space straight k with hat on top right parenthesis space plus space straight lambda left parenthesis 3 straight i with hat on top space plus space 2 straight j with hat on top space minus space 8 straight k with hat on top right parenthesis
Taking straight r with rightwards arrow on top space equals space straight x space straight i with hat on top space plus space straight y space straight j with hat on top space plus space straight z space straight k with hat on top comma space the equation of line is
               straight x straight i with hat on top space plus space straight y straight j with hat on top space plus space straight z straight k with hat on top space equals space left parenthesis 5 plus 3 straight lambda right parenthesis space straight i with hat on top space plus space left parenthesis 2 plus 2 straight lambda right parenthesis space straight j with hat on top space plus space left parenthesis negative 4 minus 8 space straight lambda right parenthesis space straight k with hat on top
Comparing the coefficients of straight i with hat on top comma space straight j with hat on top comma space straight k with hat on top comma space we get,
                        straight x space equals 5 plus 3 straight lambda comma space space straight y space equals space 2 plus 2 straight lambda comma space space space straight z space equals space minus 4 minus 8 straight lambda
or              fraction numerator straight x minus 5 over denominator 3 end fraction space equals space fraction numerator straight y minus 2 over denominator 2 end fraction space equals space fraction numerator straight z plus 4 over denominator negative 8 end fraction space equals space left parenthesis straight lambda right parenthesis
which is cartesian equation of line. 

Some More Questions From Three Dimensional Geometry Chapter

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