Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2004 — Part 02 Question 60

Math Olympiad Vault · MathNet 2004 — Part 02

Question 60

A lamp, which is supposed to be point-like, is placed at a point $V$. It projects onto a plane $a$ located 2 meters from $V$ a beam of light having the shape of a circular cone with an axis perpendicular to $a$, whose generators form an angle of $30^{\circ}$ with the axis of the cone. On the $a$ plane, in the center of the base of the cone, a cardboard cube is placed, with an edge of 1 meter. We ask what the total area illuminated by the lamp is (on the $a$ plane and on the upper face of the cube), expressed in $\mathrm{m}^{2}$.
  1. $\frac{2}{\sqrt{3}}-\frac{\pi}{9}$
  2. $4 \frac{\pi}{3}-3$
  3. $\frac{\pi}{9}-\frac{1}{\sqrt{3}}$
  4. $\pi-\sqrt{3}$
  5. $\frac{4 \pi}{9}-\frac{1}{2 \sqrt{3}}$.