NCERT Class 12-Mathematics: Chapter –11 Three Dimensional Geometry Part 10

Doorsteptutor material for IEO Class-7 is prepared by world's top subject experts: fully solved questions with step-by-step explanation- practice your way to success.

Question 24:

Find the equation of the plane through the intersection of the planes and, whose perpendicular distance from origin is unity.



Question 25:

Show that the points and are equidistant from the plane and lies on opposite side of it.


To show that these given points are equidistant from the plane , we first out the mid-point of the points which is .

On substituting by the mid-point in plane, we get


Hence, the two points lie on opposite sides of the plane are equidistant from the plane.

Question 26:

are two vectors. The position vectors of the points A and C are respectively. Find the position vector of a point P on the line AB and a point Q on the line CD such that is perpendicular to and both.


Question 27:

Show that the straight lines whose direction cosines are given by and are at right angles.


We have,


Eliminating from the both equations, we get

Thus, the direction ratios of two lines are proportional to

Also, the vectors parallel to these lines are respectively,

Question 28:

If are the direction cosines of three mutually perpendicular lines, prove that the line whose direction cosines are proportional to makes equal angles with them.



Also, let are the angles between


So, the line whose direction cosines are proportional to make equal to angles with the three mutually perpendicular lines whose direction cosines are respectively.

Objective Type Questions

Choose the Correct Answer from the Given Four Options in Each of the Exercises from 29 to 36

Question 29:

Distance of the point from axis is





Answer: (D)