1. Trigonometry – Graphs & curves The Sine curve
A sine wave is formed by plotting values of sine θ against θ.
The base (x axis) is the angle θ and the equivalent sine values are obtained from tables of calculator.
A simple sin plot illustrates the +/- quadrant relationship seen earlier

2. Trigonometry – Graphs & curves The Sine curve
In the first quadrant as θ increases from 0° to 90°, sin θ increases from 0 to 1
In the second quadrant as θ increases from 90° to 180°, sin θ decreases from 1 to 0
In the third quadrant as θ increases from 180° to 270°, sin θ decreases from 0 to -1
In the fourth quadrant as θ increases from 270° to 360°, sin θ increases from -1 to 0

3. Trigonometry – Graphs & curves The Cosine curve
A cosine wave is formed by plotting values of cos θ against θ.
The base (x axis) is the angle θ and the equivalent cos values are obtained from tables of calculator.
A simple cos plot illustrates the +/- quadrant relationship seen earlier

4. Trigonometry – Graphs & curves The Cosine curve
In the first quadrant as θ increases from 0° to 90°, cos θ decreases from 1 to 0
In the second quadrant as θ increases from 90° to 180°, cos θ decreases from 0 to -1
In the third quadrant as θ increases from 180° to 270°, cos θ increases from -1 to 0
In the fourth quadrant as θ increases from 270° to 360°, cos θ increases from 0 to 1

5. Trigonometry – Graphs & curves The Tangent curve
A tangent wave is formed by plotting values of tan θ against θ.
The base (x axis) is the angle θ and the equivalent tan values are obtained from tables or calculator or the relationship :-
tan θ = A simple tan plot illustrates the +/- quadrant relationship
seen earlier

6. Trigonometry – Graphs & curves The Tangent curve
In the first quadrant as θ increases from 0° to 90°, tan θ increases from 0 to infinity
In the second quadrant as θ increases from 90° to 180°, tan θ increases from minus infinity to 0
In the third quadrant as θ increases from 180° to 270°, tan θ increases from 0 to infinity
In the fourth quadrant as θ increases from 270° to 360°, tan θ increases from minus infinity to 0

7. Trigonometry – Angles in a quadrant
When plotting the graphs present the data values in a table as below
Increase the number of data values to improve accuracy of plot
Increase data points – for manual plot use 30° increments
For Msoft EXCEL use 10° increments (convert into Radians first)
Plot the three graphs as individual items with titles on each plot
Angle θ 0°
90°
180°
270°
360°
sin θ
cos θ
tan θ