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Ganita Manjari ยท Chapter 1.3

Where's the Point?

Drag the sliders to move the dot and watch its address on the line โ€” or the plane โ€” update live.

x = 0
at the origin
x value
0
OriginThe point 0 is called the origin โ€” the starting mark every distance is measured from.
Positive sideSlide right and x grows โ€” every point to the right of 0 is positive.
Negative sideSlide left and x shrinks below 0 โ€” every point to the left is negative.

A number line only needs ONE number to say exactly where a point is.

P = (0, 0)
at the origin
x-axis โ†’
0
y-axis โ†‘
0
Origin O = (0,0)Where the x-axis and y-axis cross. Every point is measured from here.
Quadrant I (+, +)Top-right. Both x and y are positive.
Quadrant II (โˆ’, +)Top-left. x is negative, y is positive.
Quadrant III (โˆ’, โˆ’)Bottom-left. Both x and y are negative.
Quadrant IV (+, โˆ’)Bottom-right. x is positive, y is negative.
Dashed linesDrop straight down to the x-axis and across to the y-axis โ€” those two numbers are the coordinates.

A coordinate plane needs TWO numbers, (x, y), to say exactly where a point is.

Point A
Point B
Horizontal leg (ฮ”x)
Vertical leg (ฮ”y)
Distance (hypotenuse)
A = (-3, -2)
B = (4, 3)
d โ‰ˆ 0
Ax
-3
Ay
-2
Bx
4
By
3
d = โˆš( (xโ‚‚ โˆ’ xโ‚)ยฒ + (yโ‚‚ โˆ’ yโ‚)ยฒ )
d = โˆš( (7)ยฒ + (5)ยฒ )
d = โˆš( 49 + 25 )
d = โˆš74
d โ‰ˆ 8.6
Horizontal legMove from A to B along x only: ฮ”x = xโ‚‚ โˆ’ xโ‚. This is one leg of a right triangle.
Vertical legMove from B's x-line up to B along y only: ฮ”y = yโ‚‚ โˆ’ yโ‚. This is the other leg.
Pythagoras does the restThe segment AB is the hypotenuse, so dยฒ = ฮ”xยฒ + ฮ”yยฒ โ€” just like any right triangle.

Drag any slider and watch the right triangle โ€” and the formula below it โ€” update together.

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