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Perplex
Perplex
Dashboard
Topics
Exponents & LogarithmsApproximations & ErrorSequences & SeriesMatricesComplex NumbersFinancial Mathematics
Cartesian plane & linesFunction TheoryModellingTransformations & asymptotes
2D & 3D GeometryVoronoi DiagramsTrig equations & identitiesVectorsGraph Theory
ProbabilityDescriptive StatisticsBivariate StatisticsDistributions & Random VariablesInference & Hypotheses
DifferentiationIntegrationDifferential Equations
Review VideosFormula BookletMy Progress
BlogLanding Page
Sign UpLogin
Perplex
IB Math AIHL
/
Cartesian plane & lines
/
Skills
Edit

Skill Checklist

Track your progress across all skills in your objective. Mark your confidence level and identify areas to focus on.

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

IB Math AIHL
/
Cartesian plane & lines
/
Skills
Edit

Skill Checklist

Track your progress across all skills in your objective. Mark your confidence level and identify areas to focus on.

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Skill Checklist

Track your progress across all skills in your objective. Mark your confidence level and identify areas to focus on.

14 Skills Available

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Distance, Midpoint, & Gradient

5 skills
Cartesian Plane
2. Prior learning

The Cartesian Plane is ​2​ dimensional surface, where positions represent coordinates of the form ​(x,y). The cartesian plane has

  • an ​x​-axis: a horizontal line where ​y=0​

  • a ​y​-axis: a vertical line where ​x=0.

  • the origin: where the two axes meet. Both ​x​ and ​y​ are zero here, so its coordinates are ​(0,0)​

The coordinates ​(x,y)​ of a point tell you how far along the ​x​-axis the point is, and how far along the ​y​-axis the point is. By convention, positive ​x​ coordinates are to the right of the origin, and positive ​y​-coordinates above the origin. Similarly, negative ​x​ and ​y​ coordinates are to the left of and below the origin, respectively.

Cartesian quadrants
2. Prior learning

The ​x​ and ​y​ axes divide the coordinate plane into ​4​ regions called quadrants. They are often labeled with roman numerals ​I,II,III​ and ​IV. 

Quadrant

​x​

​y​

​I​

positive

positive

​II​

negative

positive

​III​

negative

negative

​IV​

positive

negative

Distance between 2 points
2. Prior learning

The distance between two points ​(x1​,y1​)​ and ​(x2​,y2​)​ is given by

​
d=√(x1​−x2​)2+(y1​−y2​)2​📖
​
Midpoint of 2 points
2. Prior learning

The coordinates of the midpoint of two points is

​
(2x1​+x2​​,2y1​+y2​​)📖
​


Slope as rise over run
SL Core 2.1

The gradient of the line is a measure of its steepness. It is calculated by measuring the rise (change in ​y​) in the line over a certain run (change in ​x​).


The gradient of the line passing through the points ​(x1​,y1​)​ and ​(x2​,y2​)​ is

​
m=x2​−x1​y2​−y1​​📖
​


Equations of a Line

5 skills
Gradient-intercept form
SL Core 2.1

A straight line is defined by its gradient and its ​y​-intercept. The gradient-intercept equation of a line is thus:

​
y=mx+c📖
​
Point-gradient form
SL Core 2.1

If we know a point ​(x1​,y1​)​ on a line and the gradient ​m​ of the line, we can use the point-gradient form of the line:

​
y−y1​=m(x−x1​)📖
​
Vertical lines
SL Core 2.1

A vertical line does not have a well defined gradient, since there is no "run" - the ​x​-values never change.


We cannot write the equation of a vertical line in the form ​y=⋯. Instead we write

​
x=k
​

for some constant ​k.

Horizontal lines
SL Core 2.1

A horizontal line has gradient ​m=0. It is therefore in the form

​
y=c
​

for some constant ​c.

Standard form of a line
SL Core 2.1

The equation of a straight line can also be given in the form

​
ax+by+d=0📖
​


This reduces to

​
y=−ba​x−bd​
​


In examinations, you may be asked to write the equation of a line in standard form.

Line Intersections & Systems of Equations

4 skills
Parallel lines
SL Core 2.1

Two lines are parallel when they have the same gradient ​m​ and they do not intersect:

​
m1​x+c1​∥m2​x+c2​⇔m1​=m2​ and c1​=c2​
​

In this case, the system of equations formed by the two lines has no solutions.


If the lines have the same gradient and they intersect, then they must be the same line.

Intersections of straight lines
SL Core 2.1

Suppose we have the straight lines ​y=3x−2​ and ​y=2−3x. Where do the lines intersect?


Lines intersect when they have a point in common. That is, for some ​x:

​
3x−2=2−3x
​

Rearranging gives

​
6x=4⇒x=32​
​


If two lines do not intersect, then they must be parallel, since the definition of parallel is two straight lines that never meet.


If two lines are the same (possibly in different forms), then their intersection will all real numbers.

Perpendicular Lines
SL Core 2.1

Two lines are perpendicular if they form a right angle with respect to each other. In this case, the rise of one line becomes the run of the other, with a sign change:

​
m1​×m2​=−1
​
Systems of equations with 2 unknowns
SL Core 2.1

We can solve a system of  ​2​ equations and ​2​ unknowns with different methods.

​
{3y+2x−2=03y−3x+1=0​
​


By substitution

Rearranging

​
3y+2x−2=0⇒y=−32​x+32​
​


Substituting this into ​3y−3x+1=0:

​
(−2x+2)−3x+1=0
​
​
−5x=−3
​

So ​x=53​, which implies ​y=−32​⋅53​+32​=154​. So the intersection is ​(53​,154​).


By elimination

We can eliminate ​y​ from the equations by subtracting the second from the first:

​
(3y+2x−2)−(2y−3x+1)2x−2+3x−15x​=0=0=3​
​

So ​x=53​⇒y=154​​ and the intersection is again ​(53​,154​).


We can use either of these methods to systems of equations with 2 equations and 2 unknowns.

Skill Checklist

Track your progress across all skills in your objective. Mark your confidence level and identify areas to focus on.

14 Skills Available

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Track your progress:

Don't know

Working on it

Confident

📖 = included in formula booklet • 🚫 = not in formula booklet

Distance, Midpoint, & Gradient

5 skills
Cartesian Plane
2. Prior learning

The Cartesian Plane is ​2​ dimensional surface, where positions represent coordinates of the form ​(x,y). The cartesian plane has

  • an ​x​-axis: a horizontal line where ​y=0​

  • a ​y​-axis: a vertical line where ​x=0.

  • the origin: where the two axes meet. Both ​x​ and ​y​ are zero here, so its coordinates are ​(0,0)​

The coordinates ​(x,y)​ of a point tell you how far along the ​x​-axis the point is, and how far along the ​y​-axis the point is. By convention, positive ​x​ coordinates are to the right of the origin, and positive ​y​-coordinates above the origin. Similarly, negative ​x​ and ​y​ coordinates are to the left of and below the origin, respectively.

Cartesian quadrants
2. Prior learning

The ​x​ and ​y​ axes divide the coordinate plane into ​4​ regions called quadrants. They are often labeled with roman numerals ​I,II,III​ and ​IV. 

Quadrant

​x​

​y​

​I​

positive

positive

​II​

negative

positive

​III​

negative

negative

​IV​

positive

negative

Distance between 2 points
2. Prior learning

The distance between two points ​(x1​,y1​)​ and ​(x2​,y2​)​ is given by

​
d=√(x1​−x2​)2+(y1​−y2​)2​📖
​
Midpoint of 2 points
2. Prior learning

The coordinates of the midpoint of two points is

​
(2x1​+x2​​,2y1​+y2​​)📖
​


Slope as rise over run
SL Core 2.1

The gradient of the line is a measure of its steepness. It is calculated by measuring the rise (change in ​y​) in the line over a certain run (change in ​x​).


The gradient of the line passing through the points ​(x1​,y1​)​ and ​(x2​,y2​)​ is

​
m=x2​−x1​y2​−y1​​📖
​


Equations of a Line

5 skills
Gradient-intercept form
SL Core 2.1

A straight line is defined by its gradient and its ​y​-intercept. The gradient-intercept equation of a line is thus:

​
y=mx+c📖
​
Point-gradient form
SL Core 2.1

If we know a point ​(x1​,y1​)​ on a line and the gradient ​m​ of the line, we can use the point-gradient form of the line:

​
y−y1​=m(x−x1​)📖
​
Vertical lines
SL Core 2.1

A vertical line does not have a well defined gradient, since there is no "run" - the ​x​-values never change.


We cannot write the equation of a vertical line in the form ​y=⋯. Instead we write

​
x=k
​

for some constant ​k.

Horizontal lines
SL Core 2.1

A horizontal line has gradient ​m=0. It is therefore in the form

​
y=c
​

for some constant ​c.

Standard form of a line
SL Core 2.1

The equation of a straight line can also be given in the form

​
ax+by+d=0📖
​


This reduces to

​
y=−ba​x−bd​
​


In examinations, you may be asked to write the equation of a line in standard form.

Line Intersections & Systems of Equations

4 skills
Parallel lines
SL Core 2.1

Two lines are parallel when they have the same gradient ​m​ and they do not intersect:

​
m1​x+c1​∥m2​x+c2​⇔m1​=m2​ and c1​=c2​
​

In this case, the system of equations formed by the two lines has no solutions.


If the lines have the same gradient and they intersect, then they must be the same line.

Intersections of straight lines
SL Core 2.1

Suppose we have the straight lines ​y=3x−2​ and ​y=2−3x. Where do the lines intersect?


Lines intersect when they have a point in common. That is, for some ​x:

​
3x−2=2−3x
​

Rearranging gives

​
6x=4⇒x=32​
​


If two lines do not intersect, then they must be parallel, since the definition of parallel is two straight lines that never meet.


If two lines are the same (possibly in different forms), then their intersection will all real numbers.

Perpendicular Lines
SL Core 2.1

Two lines are perpendicular if they form a right angle with respect to each other. In this case, the rise of one line becomes the run of the other, with a sign change:

​
m1​×m2​=−1
​
Systems of equations with 2 unknowns
SL Core 2.1

We can solve a system of  ​2​ equations and ​2​ unknowns with different methods.

​
{3y+2x−2=03y−3x+1=0​
​


By substitution

Rearranging

​
3y+2x−2=0⇒y=−32​x+32​
​


Substituting this into ​3y−3x+1=0:

​
(−2x+2)−3x+1=0
​
​
−5x=−3
​

So ​x=53​, which implies ​y=−32​⋅53​+32​=154​. So the intersection is ​(53​,154​).


By elimination

We can eliminate ​y​ from the equations by subtracting the second from the first:

​
(3y+2x−2)−(2y−3x+1)2x−2+3x−15x​=0=0=3​
​

So ​x=53​⇒y=154​​ and the intersection is again ​(53​,154​).


We can use either of these methods to systems of equations with 2 equations and 2 unknowns.