Trigonometry · Radians and the unit circle
How to Convert Degrees to Radians
Problem
Answer
Radians measure angles with the radius as the unit. A full turn is 2pi radians, which is the same as 360 degrees.
Step-by-step solution
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Multiply the degrees by pi/180.
Why: A full turn is 360 degrees or 2pi radians, so the factor between them is pi/180.
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Multiply the numbers.
Why: The degree symbols cancel.
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Simplify the fraction by 45.
Why: 135 divided by 45 is 3, and 180 divided by 45 is 4.
Common mistakes
- Multiplying by 180/pi instead of pi/180.
- Leaving the degree symbol in the answer. Radians have no unit symbol.
- Simplifying the pi away. Pi stays in the answer.
Practice problems
Use the same method. Work each problem on paper, then open the answer to check.
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