Trig Graphs and Four Quadrants - Solving Trig Equations | Maths Tutorials from an Oxford Graduate

Learn all about the sine, cosine and tangent graphs with an Oxford graduate. In this lesson, we look at where the sin, cos and tan graphs come from and the key features. We then look at how we can use the graphs to find angles when using trigonometry.

As the graphs are cyclic and repeat, there is always more than one possible solution when using the inverse trig functions. However, a caculator will only give you one of the solutions. After discussing why this happens, we look at how we can use a basic sketch of the graph to calculate the other possible solutions.

The lesson then moves on to looking at the four quadrant method. This is another method for finding the alternative angles. We look at how this method relates to the graphs and how we could use this method instead of using the graphs.

If you want to watch a specific part of the lesson, click on the following links to take you to the relevant part of the video:
Where a sin graph comes from: 00:24
Key points on a sin graph: 05:44
Where a cos graph comes from: 06:30
Key points on a cos graph: 09:50
Comparison of sin graph and cos graph: 10:13
Where a tan graph comes from: 11:44
Key features on a tan graph: 14:56
How to use the graphs to find angles: 15:58
How to use the sine graph: 18:45
How to use the cos graph: 22:52
How to use the tan graph: 25:04
Test yourself: 27:17
How to use the four quadrants for trigonometry: 30:17
Test yourself: 40:42

Previous knowledge required:
Solving equations: (coming soon)
Basic trigonometry:    • Trigonometry - how to use SOHCAHTOA |...  
An understanding of graphs

Where to go next:
Trigonometric waveforms: (coming soon)
Solving trigonometric equations: (coming soon)
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