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Question

What is the area of a square whose diagonal measures 4 cm?

This question was previously asked in
RRB ALP/Technician 2018 CBT 2 Electronics Mechanic Question Paper (23-Jan-2019) (Shift 1)
The correct answer is
8 cm$^2$

Calculate Square Area from Diagonal

To find the area of a square given its diagonal, we can use a direct formula derived from the Pythagorean theorem.

Square Properties and Formula

Let 's' be the side length of the square and 'd' be the diagonal length. In a square, the diagonal divides it into two right-angled isosceles triangles. Applying the Pythagorean theorem (\(a^2 + b^2 = c^2\)):

  • \(s^2 + s^2 = d^2\)
  • \(2s^2 = d^2\)

The area of the square (A) is \(s^2\). Substituting A into the equation:

  • \(2A = d^2\)
  • \(A = \frac{d^2}{2}\)

Area Calculation

Given the diagonal \(d = 4\) cm:

  • Substitute the value of the diagonal into the formula: \(A = \frac{(4 \text{ cm})^2}{2}\)
  • Calculate the square of the diagonal: \(A = \frac{16 \text{ cm}^2}{2}\)
  • Compute the final area: \(A = 8 \text{ cm}^2\)

Therefore, the area of the square is 8 cm\(^2\).

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Important Questions from Plane Figures

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