The distance between
two points in 3 dimensions is found by the formula:

d^2=(x_1-x_2)^2+(y_1-y_2)^2+(z_1-z_2)^2

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## Glossary

### union

The union of two sets A and B is the set containing all the elements of A and B.

**Full Glossary List**

More in this topic

1 Magnitude 4

2 2D add and subtract

3 Distance between two points

4 Intersection with a circle

5 2D add and subtract 2

6 3D add and subtract

7 Multiplication by a scalar 2

8 Unit vectors

9 Unit vectors 2

10 Unit vectors 3

11 Equations of lines

12 Equations of lines 2

13 Equations of lines 3

14 Equations of lines 4

15 Equations of lines 5

16 Intersecting lines

17 Area of a triangle

18 Area of a triangle 2

19 Vector to cartesian form

20 Scalar product

21 Angle between vectors

22 Angle between vectors 2

23 Angle between 2D lines

24 Angle between 2D lines 2

25 Angle between 3D lines

26 Foot of perpendicular

27 Perpendicular vectors

28 Perpendicular vectors 2

29 Perpendicular vectors 3

30 Perpendicular vectors 4

31 Perpendicular lines

32 Perpendicular lines 2

33 Collinear points

34 Memorise the formulae

35 Diagonals of a parallelogram

36 Extended problem 1

37 Extended problem 2

38 Sequence O-test

39 O-test 1

40 O-test 2

41 O-test 3

42 O-test 4

43 O-test 5

44 O-test 6

45 O-test 7

46 O-test 8

47 Exam O-test 1

48 Exam O-test 2

49 Exam O-test 3

50 Exam O-test 4

51 Exam O-test 5

52 Exam timed O-test

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