AQA A Level Maths: Pure復習筆記5.1.1 Trigonometry - Definitions
Trigonometry - Definitions
What is trigonometry?
- Trigonometry looks at the relationship between side lengths and angles of triangles
- It comes from the Greek words trigonon meaning ‘triangle’ and metron meaning ‘measure’
- The three trigonometric functions Sine, Cosine and Tangent come from ratios of side lengths in right angled triangles
What is the unit circle and how does it help with trigonometry?
- The unit circle is a circle with radius 1 and centre (0,?0)
- It can be used to calculate trig values as a co?ordinate point (x,?y) on the circle
- (x,?y) = (cos θ, sin θ), where θ is the angle measured anticlockwise from the positive x?axis
- It allows us to calculate?sin,?cos?and?tan?for angles greater than 90°
Worked Example
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