Coordinate Plane Strategy

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

by phoenix9801 » Sun Jul 22, 2012 11:40 pm

Hello, I have a quick question. Please refer to the Image below. Hence please explain step by step instruction for clarifications. Greatly appreciate it.

Question 1: how did they get 8 as a y-coordinate and 6 x-coordinate as an answer.
Slop = y^2 - y^1 / x^2 - x^1 =
3 - (-5) = 8
1 - 7 = -6
Hence, I don't understand why is it 6 when it supposed to be negative -6 right?

Question 2: How to you allays know which side is a, b, or c? is the Y-coordinate is always the height and x-coordinate is always the base?

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Source: Beat The GMAT — Problem Solving | Sun Jul 22, 2012 11:40 pm

das.ashmita: Master | Next Rank: 500 Posts; Posts: 118; Joined: Mon May 21, 2012 10:07 pmFollowed by: 4 members; Thanked: 23 times

by das.ashmita » Mon Jul 23, 2012 1:04 am

Hi phoenix9801

In the given solution, they are not calculating the slope.
They are calculating the length of the base and height of the right angled triangle.

Hence the sign won't matter.

base = |x2-x1|= |3-(-5)| =8
height = |y2-y1| = |1-7| = 6

For the 2nd question, it doesn't matter which side of the triangle you take as base. But it's advisable to chose |x2-x1| as the base for better understanding.

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niketdoshi123: Master | Next Rank: 500 Posts; Posts: 210; Joined: Thu Mar 08, 2012 11:24 pmFollowed by: 3 members; Thanked: 62 times

by niketdoshi123 » Mon Jul 23, 2012 1:22 am

phoenix9801 wrote: Question 2: How to you allays know which side is a, b, or c? is the Y-coordinate is always the height and x-coordinate is always the base?

Here points a,b & c are just the notations, you can use them to represent any of the sides of the triangle.
Here the co-ordinate plane represents a 2-dimensional plane system, where the coordinates of a point are a pair of numbers that define its exact location on a 2-dimensional plane.
The co-ordinates of a point are written as an ordered pair. for example a(4,5), b(6,2) etc
Let a(x,y)
"x" specifies how far along the x (horizontal) axis the point is.
"y" specifies how far up or down the y (vertical) axis to go.
all are in respect to the origin where O(x,y) = O(0,0).

Slop = y^2 - y^1 / x^2 - x^1 =

Here the notation is wrong
Slop = y2 - y1/ x2 - x1

The question is asking you to find the distance between the two points not the slope of the line, they(the distance b/w two points and the slope of the line) are not same.

The distance can be calculated using the pythagoras' theorem.

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