Points and Vectors

From GeoGebra Manual
Jump to: navigation, search


Points and vectors may be entered via Input Bar in Cartesian or polar coordinates (see Numbers and Angles). Points can also be created using Mode point.svg Point tools and vectors can be created using the Mode vectorfrompoint.svg Vector from Point Tool or the Mode vector.svg Vector Tool and a variety of commands.

Note: Upper case labels denote points, whereas lower case labels refer to vectors. This convention is not mandatory.
Example:
  • To enter a point P or a vector v in Cartesian coordinates you may use P = (1, 0) or v = (0, 5).
  • To enter a point in the Menu view spreadsheet.svg Spreadsheet View, name it using its cell address, e.g.: A2 = (1, 0)
  • To enter a point in polar coordinates type in P = (1; 0°) or v = (5; 90°).
Note: You need to use a semicolon to separate polar coordinates. If you don’t type the degree symbol, GeoGebra will treat the angle as if entered in radians.


Coordinates of points and vectors can be accessed using predefined functions x() and y().

Example: If P=(1,2) is a point and v=(3,4) is a vector, x(P) returns 1 and y(v) returns 4.
Note: Polar coordinates of point Q can be obtained using abs(Q) and arg(Q).

Calculations

In GeoGebra, you can also do calculations with points and vectors.

Example:
  • You can create the midpoint M of two points A and B by entering M = (A + B) / 2 into the Input Bar.
  • You may calculate the length of a vector v using length = sqrt(v * v) or length = Length(v)
  • If A = (a, b), then A + 1 returns (a + 1, b + 1). If A is a complex number a+bί, then A+1 returns a + 1 + bί.

Vector Product

Let (a, b) and (c, d) be two points or vectors. Then (a, b) ⊗ (c, d) returns the z-coordinate of vector product (a, b, 0) ⊗ (c, d, 0) as single number.

Similar syntax is valid for lists, but the result in such case is a list.

Example:
  • {1, 2} ⊗ {4, 5} returns {0, 0, -3}
  • {1, 2, 3} ⊗ {4, 5, 6} returns {3, 6, -3}.
© 2019 International GeoGebra Institute