Calculus I

The 8-ft wall shown here stands 27 ft from the building. Find the lenght of the shortest straight beam that will reach to tthe side of the building from the ground outside the wall.
ANSWER 46.87ft
How do i solve???

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  1. Use similar triangles. Let x be the length from the wall to the point the board touches the ground.

    Length/(27+x)= sqrt(64+x^2)/x
    from similar triangles.

    Length= (27+x)/x * sqrt(64+x^2)

    Now, find dL/dx and set to zero. Solve for x. Watch your algebra.

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    bobpursley
  2. No, it's 9001

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