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### Course: Class 9 (Foundation)>Unit 8

Lesson 1: Intro to the coordinate plane

# Introduction to the coordinate plane

When we use coordinates to locate a point on a coordinate plane, we use two numbers to specify the horizontal (x) and vertical (y) positions. The first number in a coordinate pair tells us how far to move left or right from the origin, while the second number tells us how far to move up or down.

## Want to join the conversation?

• Why do you need to say the X axis first, and then the Y axis?
• Because if people changed it back and forth, people would get very different graphs
• why is there only a Y and X coordinate istead of random letters?
• On a 2 dimensional plane, the axes are named x and y, hence there are only x and y coordinates. On a 3D plane, you would also have a z coordinate. You can also look at it from an algebraic perspective where when you are comparing 2 equations, x and y are generally used as the two variables for graphing linear equations
• can there be coordinate planes in 3D (like X Y Z)?
• Yes, imagine being in a square room, one of the corners could be an origin, so the floor is the xy plane (where z=0), but you could locate any point in the room (such as making the units in feet) by being an x, y, and z distance from this origin. To get really fancy, the adjacent room or the hallway might be considered negative numbers depending on where they are related to the origin (a basement might be negative in the z direction).
• why does the x and y axis have to be in a spacifice spot?
• In math,the x-axis must be horizontal & the y-axis has to be vertical,or you probably would end up with a whole different situation.
• Why does the coordinate start with the x-axis and not the y-axis?
• This to avoid confusion. If someone was to just give you two coordinates, you would have to a ask them which number is for which axis since flipping the coordinates can give you two very different graphs
• Why does it matter how far you go to the right or the left
• Good Question!
It matters because to plot the given coordinates on the cartesian plane you have to move along the x-axis horizontally in the left or right direction and the same for the y-axis in the vertical direction.

For example, if you have to plot (3,4) on the cartesian plane you have to move 3 points to the right (because 3 is positive) and 4 points in the upward direction (because 4 is also positive). The resulting exact point where these two coordinates meet is your correct answer.

Hope this Helps!
• y axis first or x axis first confused
• Just like in the alphabets x comes before y in the same way in coordinates system the x-axis comes first and then the y-axis.
So for example in (2,3) the x-axis coordinate is 2 and the y-axis coordinate is 3.
This is extra information - x-axis is also called the abscissa and the y-axis is also called the ordinate.
• why is there only a Y and X coordinate istead of random letters?
• This is because this is on a 2D Plane where only X and Y cords exist also because this is for starters in this subject
• when do we use geometry?
Hope this helps! -`Johnny Unidas`