IB DP Maths: AA HL复习笔记3.6.4 Relationship Between Trigonometric Ratios
Relationship Between Trigonometric Ratios
What relationships between trigonometric ratios should I know?
- If you know a value for one trig ratio you can often use this to work out the value for the others without needing to find θ
-
How do we determine whether a trigonometric ratio will be positive or negative?
- It is possible to determine whether a trigonometric ratio will be positive or negative by looking at the size of the angle and considering the unit circle
- Angles in the range 0° < θ° < 90° will be positive for all three ratios
- Angles in the range 90° < θ° < 180° will be positive for sin and negative for cos and tan
- Angles in the range 180° < θ° < 270° will be positive for tan and negative for sin and cos
- Angles in the range 270° < θ° < 360° will be positive for cos and negative for sin and tan
- The ratios for angles of 0°, 90°, 180°, 270° and 360° are either 0, 1, -1 or undefined
- You should know these ratios or know how to derive them without a calculator
Exam Tip
- Being able to sketch out the unit circle and remembering CAST can help you to find all solutions to a problem in an exam question
Worked Example
转载自savemyexams
国际竞赛真题资料-点击免费领取！
美高学分项目重磅来袭！立即了解
AMC8备考管家服务全新上线！
