# Class 11 NCERT Solutions- Chapter 12 Introduction to three dimensional Geometry – Exercise 12.1

• Difficulty Level : Medium
• Last Updated : 04 Jan, 2021

### Problem 1: A point is on the x-axis. What are its y coordinate and z-coordinates?

Solution:

If a point is on the x-axis, then the coordinates of y and z are 0.

Attention reader! All those who say programming isn't for kids, just haven't met the right mentors yet. Join the  Demo Class for First Step to Coding Coursespecifically designed for students of class 8 to 12.

The students will get to learn more about the world of programming in these free classes which will definitely help them in making a wise career choice in the future.

So the point is (x, 0, 0)

### Problem 2: A point is in the XZ-plane. What can you say about its y-coordinate?

Solution:

If a point is in XZ plane,

So its y-coordinate is 0

### (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:

(i) (1, 2, 3)

Here x is positive, y is positive and z is positive.

So it lies in I octant.

(ii) (4, -2, 3)

Here x is positive, y is negative and z is positive.

So it lies in IV octant.

(iii) (4, -2, -5)

Here x is positive, y is negative and z is negative.

So it lies in VIII octant.

(iv) (4, 2, -5)

Here x is positive, y is positive and z is negative.

So it lies in V octant.

(v) (-4, 2, -5)

Here x is negative, y is positive and z is negative.

So it lies in VI octant.

(vi) (-4, 2, 5)

Here x is negative, y is positive and z is positive.

So it lies in II octant.

(vii) (-3, -1, 6)

Here x is negative, y is negative and z is positive.

So it lies in III octant.

(viii) (2, -4, -7)

Here x is positive, y is negative and z is negative.

So it lies in VIII octant.

### (i) The x-axis and y-axis taken together determine a plane known as _______.

Solution:

The x-axis and y-axis taken together determine a plane known as XY Plane.

### (ii) The coordinates of points in the XY-plane are of the form _______.

Solution:

The coordinates of points in the XY-plane are of the form (x, y, 0).

### (iii) Coordinate planes divide the space into ______ octants.

Solution:

Coordinate planes divide the space into eight octants.

My Personal Notes arrow_drop_up