**NCERT Solutions for Class 11 Maths Chapter 11 ****Introduction to Three Dimensional Geometry**** Ex 11.1**

**Ex 11.1 Class 11 Maths Question 1.**

A point is on the x-axis. What are its y-coordinates and z-coordinates?

**Solution:**

In three-dimensional geometry, the coordinates of any point on the x-axis are of the form (x, 0, 0). Thus, the y-coordinate and the z-coordinate of the given point is zero (0).

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**Ex 11.1 Class 11 Maths Question 2.**

A point is in the XZ-plane. What can you say about its y-coordinate?

**Solution:**

In three-dimensional geometry, the coordinates of any point in XZ-plane are of the form (x, 0, z). Thus, the y-coordinate of the given point is zero (0).

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**Ex 11.1 Class 11 Maths Question 3.**

Name the octants in which the following points lie:

(1, 2, 3), (4, -2, 3), (4, -2, -5), (4, 2, -5), (-4, 2, -5), (-4, 2, 5), (-3, -1, 6), (-2, -4, -7)

**Solution:**

The point (1, 2, 3) lies in Octant I.

The point (4, -2, 3) lies in Octant IV.

The point (4, -2, -5) lies in Octant VIII.

The point (4, 2, -5) lies in Octant V.

The point (-4, 2, -5) lies in Octant VI.

The point (-4, 2, 5) lies in Octant II.

The point (-3, -1, 6) lies in Octant III.

The point (-2, -4, -7) lies in Octant VII.

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**Ex 11.1 Class 11 Maths Question 4.**

**Fill in the blanks:****(i)** The x-axis and y-axis taken together determine a plane known as ______.**(ii)** The coordinates of points in the XY-plane are of the form _______.**(iii)** Coordinate planes divide the space into ______ octants.

**Solution:****(i)** XY-plane**(ii)** (x, y, 0)**(iii)** eight

**Related Links:**

**NCERT Solutions for Maths Class 9**