Maths · Class 11 · Chapter 11
Introduction to Three Dimensional Geometry
10 lessons 79 min 2 simulations
This chapter adds a third coordinate to the coordinate geometry of the plane. Three mutually perpendicular axes meet at the origin and carry three coordinate planes, which split space into eight octants whose names follow the signs of x, y and z. A point is located by its perpendicular distances from the three planes, and the distance between two points comes from Pythagoras applied twice across a box. That one formula then settles collinearity, right angles, parallelograms and the equations of sets of points, and averaging the vertices gives a centroid.
What the exam asks
For JEE Main, this short chapter is a foundation: the octant signs, the forms of points on axes and planes, and the distance formula are used again in vectors and in the three dimensional geometry of class 12. Most losses come from a wrong sign in a coordinate difference, from confusing the plane a coordinate is measured from, and from adding unsimplified surds in collinearity tests. Section formula, direction cosines and planes are not in this rationalised chapter; they appear in class 12.
Lessons
10 lessons · 79 min
1Why a point needs three numbersNCERT §11.16 min2Coordinate axes and coordinate planesNCERT §11.26 min3The eight octantsNCERT §11.2, Table 11.111 min 1 sim4Coordinates of a point in spaceNCERT §11.37 min5Points on axes and planesNCERT §11.3 Note, Examples 1-26 min6Distance between two pointsNCERT §11.4, Example 311 min 1 sim7Testing collinearity and right anglesNCERT §11.4, Examples 4-57 min8Equations of sets of pointsNCERT §11.4 Example 6, Example 87 min9Parallelograms and the centroidNCERT §11.4, Miscellaneous Examples 7-97 min10Chapter reviewMust-know facts, traps and formulas11 min