JEE MainMathematicsHeights and Distances
A vertical pole of height h stands at the centroid of a triangle ABC with side lengths a , b , and c . If the angles of elevation of the top of the pole from the vertices A , B , and C are , , and respectively, then the value of the ratio a^2+b^2+c^2 h^2 is:
Options
- A3( ^2 + ^2 + ^2 )
- B4 3 ( ^2 + ^2 + ^2 )
- C^2 + ^2 + ^2
- D1 3 ( ^2 + ^2 + ^2 )
Correct answer
A. 3( ^2 + ^2 + ^2 )
Step-by-step solution
Let the centroid of the triangle ABC be G . The vertical pole is positioned at G and has height h . The horizontal distances from the centroid to the vertices can be expressed using the angles of elevation: AG = h BG = h CG = h The distance from a vertex to the centroid is two-thirds the length of the corresponding median. For median m_a to side a : AG = 2 3 m_a AG^2 = 4 9 m_a^2 Using Apollonius's theorem, m_a^2 = 1 4 (2b^2 + 2c^2 - a^2) . Thus, AG^2 = 1 9 (2b^2 + 2c^2 - a^2) Similarly, for the other vertices: BG^2