3.4.1
Graphs of Common Functions
Common Functions
Common Functions
To sketch a graph, see if it is linear, quadratic or cubic. Then plot some x and y co-ordinates and join them up in the right shape.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Linear
Linear
- Linear functions are straight lines in the form y = mx + c.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Quadratic
Quadratic
- Quadratic functions have an x2 term.
- They are in the form y = ax2 + bx + c.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Cubic
Cubic
- Cubic functions are in the form y = ax3 + bx2 + cx + d.
- If a > 0, it starts in the bottom left and goes up to the right.
- If a < 0, it starts in the top left and goes down to the right.
Common Functions
Common Functions
To sketch a graph, look at whether it is exponential, reciprocal or some other type of graph. Then plot some x and y co-ordinates and join them up in the right shape.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Exponential
Exponential
- Exponential functions are of the form y = kx or y = k-x.
- They are completely above the x axis and go through the point (0, 1).
- If k > 1 and the power is positive then the graph starts in the bottom left and then has a steep gradient up to the top right.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Reciprocal
Reciprocal
- Reciprocal graphs never cross the x or y axis. They are only in 2 parts (quadrants) of the graph.
- They are usually y = a⁄x or xy = a.
Trigonometric Functions
Trigonometric Functions
To sketch trigonometric graphs (y = sin(x), y = cos(x), y = tan(x)) use x values which are multiples of 90° since these are the important points on the graph.


Tangent
Tangent
- tan(x) repeats every 180°
- There are vertical lines at 90°, 270°, ... because the function is undefined at these points.


sin(x)
sin(x)
- sin(x) repeats every 360°.


sin(x) and cos(x)
sin(x) and cos(x)
- cos(x) also repeats every 360°.
- They have the same wave shape but the cosine graph is shifted by 90° compared to the sine graph.
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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