why is the first quadrant positive?

Question

and why is the second quadrant negative, positive?
why is the third quadrant negative?
why is the fourth quadrant positive,negative?

Answer 1

Plain definition: on the horizontal axis, the x-axis, from the beginning (0,0), the positive direction is defined to be rightwards and the negative one to be leftwards. On the vertical axis, the y-axis, the positive direction is defined to be upwards and the negative one to be downwards.
Regards
Tonio

Answer 2

Well, the quadrants are named after the four sections of a graph, starting with the first quadrant in the upper right corner and going counterclockwise (this is because of the locations of angles with terminal sides, but that's another matter). The first quadrant lies where the x & y coordinates are both positive, the second where the x is negative, and the y is positive, and so on around the graph. That's how you know what sign certain quadrants have.

Answer 3

Its just convention. Why do american cars have the steering wheel built into the left side of the car? We just decided to do it this way, likewise the x is positive as it increases to the right, and y is positive as it increases "up" ...

In the third quadrant, both the x coordinates and the y coordinates are negative.

In the fourth quadrant, the x is positive and y is negative.

You have to draw these out to really see them, and I'm afrain I cant do that for you.

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Good Luck!

Answer 4

because all the points in the first quadrant have positive x and y values. all the points in the second quadrant have a negative x value and positive y value, and so on.

Answer 5

First one has X positive and Y positive. X*Y=positive
Second has X negative and Y positive X*Y=negative
Third has both negative X*Y=positive (negative x negative= positive)
Forth has X pozitive and Y negative.

Answer 6

I suppose it is just a matter of convention and what Descart used when he introduced the Cartisian convention.

Answer 7

cos a = x/r
sin a = y/r
tan a = y/x
Quadrant 1
x is +ve
y is +ve
r is +ve (always)
Sin,cos tan are thus all +ve
Quadrant 2
x is -ve
y is +ve
r is +ve
sin is y/r is + ve
cos is x/r is - ve
tan is y/r is - ve
Quadrant 3
x is -ve
y is -ve
r is +ve
sin is -ve
cos is -ve
tan is +ve
Quadrant 4
x is +ve
y is -ve
r is +ve
sin is -ve
cos is +ve
tan is -ve

This leads to:-
sin | all
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tan | cos