SOLUTION: The Thomas Jefferson Memorial in Washington, D.C., is a circular building with a rectangular porch. You are standing 20 meters away from the circular wall of the building and 49 me

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Question 1140200: The Thomas Jefferson Memorial in Washington, D.C., is a circular building with a rectangular porch. You are standing 20 meters away from the circular wall of the building and 49 meters away from the point of tangency. What is the radius of the circular part of the memorial?
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


The figure that can be drawn from the description of the problem is a circle of unknown radius. You are standing outside the building looking at it.

If you look at the very edge of the building from where you are, the distance to that point of the building is 49m; if you look directly towards the center of the building, the distance to the nearest point on the building is 20m.

We then have a tangent to the circle, and a secant that passes through the center of the circle.

According to a commonly used theorem, the square of the length of the tangent is equal to the product of the length of the whole secant and the length of the portion of the secant outside the circle.

Let the radius be r; then the theorem says

49%5E2+=+%2820%2B2r%29%2820%29

Solve using basic algebra to find the radius.