Example: What is the area of this rectangle?The formula is: Area = w × h We know w = 5 and h = 3, so: Area = 5 × 3 = 15 Example: What is the area of this triangle?Height = h = 12 Base = b = 20 Area = ½ × b × h = ½ × 20 × 12 = 120 We are working on learning the coordinate planes which will lead us up to our 7th grade work of beginning algebra. The plane containing the "x" axis and "y" axis Cartesian CoordinatesUsing Cartesian Coordinates we mark a point on a graph by how far along and how far up it is:
X and Y Axis
Axis: The reference line from which distances are measured. The plural of Axis is Axes, and is pronounced axeez
And you can remember which axis is which by: x is A CROSS, so x is ACROSS the page.
Like 2 Number Lines Put TogetherIt is like we put two Number Lines together, one going leftright, and the other going downup. Direction
Writing CoordinatesThe coordinates are always written in a certain order:
This is called an "ordered pair" (a pair of numbers in a special order) And usually the numbers are separated by a comma, and parentheses are put around the whole thing like this: (3,2) The OriginThe point (0,0) is given the special name "The Origin", and is sometimes given the letter "O". Abscissa and OrdinateYou may hear the words "Abscissa" and "Ordinate" ... they are just the x and y values:
"Cartesian" ... ?They are called Cartesian because the idea was developed by the mathematician and philosopher Rene Descartes who was also known as Cartesius. He is also famous for saying "I think, therefore I am". What About Negative Values of X and Y?Just like with the Number Line, you can also have negative values. Negative: start at zero and head in the opposite direction:
In Quadrant I both x and y are positive, but ...
Like this:
Note: The word Quadrant comes form quad meaning four. For example, four babies born at one birth are called quadruplets, a fourlegged animal is a quadruped. and a quadrilateral is a foursided polygon. Dimensions: 1, 2, 3 and more ...Think about this:
3 DimensionsCartesian coordinates can be used for locating points in 3 dimensions as in this example:
In fact, this idea can be continued into four dimensions and more  I just can't work out how to illustrate that for you!

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