The formula is arc length=θ(r){\displaystyle {\text{arc length}}=\theta (r)}, where θ{\displaystyle \theta } equals the measurement of the arc’s central angle in radians, and r{\displaystyle r} equals the length of the circle’s radius. You need to know the length of the radius to use this method. Make sure you substitute the length of the radius for the variable r{\displaystyle r}. For example, if the circle’s radius is 10 cm, your formula will look like this: arc length=θ(10){\displaystyle {\text{arc length}}=\theta (10)}. You should have this information in radians. If you know the angle measurement in degrees, you cannot use this method. For example, if the arc’s central angle is 2.36 radians, your formula will look like this: arc length=2.36(10){\displaystyle {\text{arc length}}=2.36(10)}. The product will be the length of the arc. For example:2.36(10){\displaystyle 2.36(10)}=23.6{\displaystyle =23.6}So, the length of an arc of a circle with a radius of 10 cm, having a central angle of 23.6 radians, is about 23.6 cm.

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Write a summary of the previous text in Vietnamese:
Lập công thức tính độ dài cung. Thay giá trị độ dài bán kính đường tròn vào công thức. Thay số đo góc ở tâm của cung vào công thức. Nhân bán kính với số đo radian.