1. Using a compass and a ruler draw three sectors of different sizes. Make sure that central angle is the same for all three.
2. Use the ruler to measure radius [[$ r $]] and bow [[$ b $]] of each sector.
3. Calculate maximum and minimum values of radius and bow using assumption that when using ruler you can measure with accuracy of 1 mm.
4. Use your calculator to get ratio [[$ \frac{b}{r} $]].
5. Calculate also ratios [[$ \frac{b_{max}}{r_{min}} $]] and [[$ \frac{b_{min}}{r_{max}} $]]. Use these to get your measurement uncertainty.
6. The value calculated is value of angle in radians. Radian unit is quite common in science.
7. Compare your three results and results of others together.