Answer:
a) [tex]\Delta A \approx 26.389\,cm^{2}[/tex], b) [tex]r_{A} \approx 0.019[/tex], c) [tex]\delta = 1.9\,\%[/tex]
Step-by-step explanation:
a) The area of the circular disk is modelled after this expression:
[tex]A = \pi \cdot r^{2}[/tex]
The total differential is given by the following formula:
[tex]\Delta A = 2\pi r \cdot \Delta r[/tex]
The maximum absolute error in the calculated area of the disk is:
[tex]\Delta A = 2\pi \cdot (21\,cm)\cdot (0.2\,cm)[/tex]
[tex]\Delta A \approx 26.389\,cm^{2}[/tex]
b) The relative error is given by:
[tex]r_{A} = \frac{\Delta A}{A}[/tex]
[tex]r_{A} = \frac{26.389\,cm^{2}}{\pi \cdot (21\,cm)^{2}}[/tex]
[tex]r_{A} \approx 0.019[/tex]
c) The percentage error is:
[tex]\delta = r_{A}\times 100\,\%[/tex]
[tex]\delta = 0.019 \times 100\,\%[/tex]
[tex]\delta = 1.9\,\%[/tex]
