-->

Three Dimensional Geometry

Question
CBSEENMA12033302

Find the equations of the line passing through the point P(–1, 3, –2) and perpendicular to the lines
straight x over 1 space equals space straight y over straight z space equals space straight z over 3 space space and space fraction numerator straight x plus 2 over denominator negative 3 end fraction space equals space fraction numerator straight y minus 1 over denominator 2 end fraction space equals space fraction numerator straight z plus 1 over denominator 5 end fraction

Solution
The equations of given lines are
                  straight x over 1 space equals space straight y over 2 space equals space straight z over 3                                        ...(1)
and          fraction numerator straight x plus 2 over denominator negative 3 end fraction space equals space fraction numerator straight y minus 1 over denominator 2 end fraction space equals space fraction numerator straight z plus 1 over denominator 5 end fraction                       ...(2)
Any line through P (– 1, 3, –2) is
fraction numerator straight x plus 1 over denominator straight l end fraction space equals space fraction numerator straight y minus 3 over denominator straight m end fraction space equals space fraction numerator straight z plus 2 over denominator straight n end fraction                                        ...(3)
where l, m, n are direction ratios of the line     
Since (3) is perpendicular to (1) and (2)
∴ l + 2 m + 3 n = 0    ...(4)
and – 3 l + 2 m + 5 n = 0    ...(5)
Solving (4) and (5), we get,
          space fraction numerator l over denominator 10 minus 6 end fraction equals space fraction numerator straight m over denominator negative 9 minus 5 end fraction equals fraction numerator straight n over denominator 2 plus 6 end fraction

therefore space space space space space straight l over 4 space equals space fraction numerator straight m over denominator negative 14 end fraction space equals space straight m over 8
rightwards double arrow space space space space space straight l over 2 space equals space fraction numerator straight m over denominator negative 7 end fraction space equals space straight n over 4
∴ from (3), the equations of line are
fraction numerator straight x plus 1 over denominator 2 end fraction space space equals space fraction numerator straight y minus 3 over denominator negative 7 end fraction space equals space fraction numerator straight z plus 2 over denominator 4 end fraction.

Some More Questions From Three Dimensional Geometry Chapter

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