figure: ar-a2-wiper.png A windscreen wiper turns about a pivot…

Step 1. The big sector. $\dfrac{1}{3} \times \dfrac{22}{7} \times 35^2 = \dfrac{3850}{3}\ \text{cm}^2$.

Step 2. The small sector. $\dfrac{1}{3} \times \dfrac{22}{7} \times 14^2 = \dfrac{616}{3}\ \text{cm}^2$.

Step 3. The difference. $\dfrac{3850 - 616}{3} = \dfrac{3234}{3} = 1078\ \text{cm}^2$.