An elliptical wing has aspect ratio $AR = 8.0$ and lift coefficient $C_L = 0.80$. What is the induced drag coefficient $C_{Di}$ of this wing? (Take $\pi \approx 3.1416$, round to three decimal places).

Answer Key:

0.025

### Solution: For an elliptical lift distribution, $C_{Di} = \frac{C_L^2}{\pi AR} = \frac{(0.80)^2}{3.1416 \times 8} = \frac{0.64}{25.1327} \approx 0.02546 \approx 0.025$. Correct: 0.025 (range 0.024 to 0.027).

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