Sigma Percentile
JEE Advanced 2000
LEVELJEE Main

Animated Solution for Mathematics - Trigonometry: A pole stands vertically inside a triangular park . If the angle of elevation of the top of the pole from each corner of the park is same, then in the foot of the pole is at the

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Visualized Solution

Visualizing the Triangular Park

  • Consider a triangular park on the ground.

Erecting the Vertical Pole

  • A vertical pole stands inside the park.
  • is the foot of the pole, and is its top.

Connecting the Foot to the Corners

  • Let's join the foot of the pole to each corner and .

The Right Angles

  • Since the pole is vertical, it is perpendicular to the ground.
  • Therefore, .

Lines of Sight

  • We look at the top of the pole from each corner and .

The Angle of Elevation

  • The problem states the angle of elevation of the top of the pole from each corner is the same.
  • Let this angle be .

Analyzing

  • In the right-angled triangle , we can apply trigonometry.

Distance from to

  • Rearranging the equation to solve for the base:

Distances from to and

  • By applying the exact same logic to and , we get:

Equating the Distances

  • Since and are all equal to , we can conclude that:

The Circumcentre

  • In a triangle, the unique point that is equidistant from all three vertices is called the Circumcentre.

Final Conclusion

  • Therefore, the foot of the pole must be located at the circumcentre of the triangular park .

The Sigma Insight: Heights and Distances

Solution Diagram

Analyzing the Setup

Imagine a triangular park situated on a horizontal plane. A vertical pole of height stands at a point on the ground, with its top at point .
Since the pole is vertical, it is perpendicular to the ground. This implies that the line segment is perpendicular to any line in the plane passing through .
Consequently, we form three right-angled triangles: , , and . In each of these triangles, the angle at is , and the height is common to all.

The Trigonometric Bridge

The problem states that the angle of elevation from each corner (, , and ) to the top of the pole is identical. Let this constant angle be denoted by .
In the right-angled triangle , we apply the definition of the tangent function:
Rearranging this expression to solve for the distance from the foot of the pole to the vertex , we obtain:
Since the height and the angle are identical for all three vertices, the same logic applies to triangles and . Therefore, we find:

The Geometric Revelation

We have arrived at the conclusion that the foot of the pole is equidistant from all three vertices of the triangular park.
In Euclidean geometry, the unique point that is equidistant from all three vertices of a triangle is defined as the circumcentre of the triangle.
Conclusion: The foot of the pole must be the circumcentre of .
This result is a powerful tool in coordinate geometry and 3D visualization. Whenever a point in space subtends the same angle of elevation to all vertices of a polygon, the projection of that point onto the plane is the circumcentre of the polygon.

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