In a right pyramid with square base of side 4 cm. The vertical edge makes an angle of 60° with the side of the base. Find the volume of the pyramid.
Explanation:
The vertical edge makes an angle of 60° with the side of the base, Let us consider the vertical triangle OAB.
In triangle OAB, the two base angles are 60°, hence the vertical angle will also be 60°. ∴ OAB is an equilateral triangle, ⇒ The slant height of the pyramid = height of triangle OAB = √3/2 × 4 = 2√3
Now, in right triangle OPQ,
OP = height of the pyramid, PQ = 4/2 = 2 OQ = 2√3.
∴ OQ2 = PO2 + PQ2 ⇒ 12 = h2 + 4 ⇒ h2 = 8 ⇒ h = 2√2
Now, Volume of pyramid = 1/3 × (base area) × (height) = 1/3 × 16 × 2√2 = 32√2/3.
Hence, option (a).
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