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How to Subtract Fractions With Pi

Pi is an important number in geometry because it is the value of the ratio of circumference of a circle in relation to the diameter. (The value can be approximated as 3.14159.) Pi is an irrational number, so it can't be expressed as a fraction, as is the case with rational numbers. (All fractions are rational numbers, with the exception of those containing 0 in the denominator or those that are under square root signs.) Sometimes, especially in trigonometry, you will need to subtract pi from fractions that also have pi in them.

Instructions

- 1
  Identify the numbers to be subtract. For example, suppose you need to subtract pi from 2pi/3. In angle measurements, pi radians corresponds to 180 degrees.
- 2
  Convert pi to a fraction. To do this, multiply it by a fraction that equals 1; this fraction will have a numerator (top number) and denominator (bottom number) that is the same as the denominator of the fraction it is being subtracted from. In the example, you would multiply pi by 3/3 to get 3pi/3.
- 3
  Subtract the fractions as normal. The final answer in the example would be 2pi/3 - 3pi/3, which equals -pi/3.

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