Machine-translated by Google. Questions are authored in English.
Top

Discussion

The area of a square is \(d\). What is the area of the circle which has the diagonal of the square as its diameter?

  • A.\(\pi d\)
  • B.\(\pi d^{2}\)
  • C.\(\frac{1}{4}\pi d^{2}\)
  • D.\(\frac{1}{2}\pi d\)

Answer: D

The area of the circle is \(\frac{1}{2}\pi d\).

Let the side of the square be \(s\), so \(s^{2} = d\). The diagonal is \(s\sqrt{2}\), and it is the diameter, so the radius is \(\frac{s\sqrt{2}}{2}\).

\[ \begin{aligned} \text{area} &= \pi \left(\frac{s\sqrt{2}}{2}\right)^{2} \\ &= \pi \cdot \frac{2s^{2}}{4} = \frac{1}{2}\pi d \end{aligned} \]

\(\pi d\) uses the diagonal as the radius, and \(\pi d^{2}\) and \(\frac{1}{4}\pi d^{2}\) treat \(d\) as a length rather than an area, so they have the wrong dimensions.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.