IB DP Maths: AA HL復習筆記3.1.2 Radian Measure
What are radians?
- Radians are an alternative to degrees for measuring angles
- 1 radian is the angle in a?sector?of radius 1 and arc length 1
- A circle with radius 1 is called a?unit circle
- Radians are normally quoted in terms of π
- 2π?radians = 360°
- π radians = 180°
- The symbol for radians is?c?but it is more usual to see?rad
- Often, when π?is involved, no symbol is given as it is obvious it is in radians
- Whilst it is okay to omit the symbol for radians, you should never omit the symbol for degrees
- In the exam you should use radians unless otherwise indicated
How do I convert between radians and degrees?
It is a good idea to remember some of these and use them to work out other conversions- Your GDC will be able to work with both radians and degrees
Exam Tip
- Sometimes an exam question will specify whether you should be using degrees or radians and sometimes it will not, if it doesn't it is expected that you will work in radians
- If the question involves π then working in radians is useful as there will likely be opportunities where you can cancel out π
- Make sure that your calculator is in the correct mode for the type of angle you are working with
Worked Example
i)? ? ?Convert 43.8° to radians.
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