SOLUTION: The ceiling in the hallway 10 m wide is in the shape of a semiellipse and is 9 m high in the center and 6 m high at the side walls. Find the height of the ceiling 2m from either

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: The ceiling in the hallway 10 m wide is in the shape of a semiellipse and is 9 m high in the center and 6 m high at the side walls. Find the height of the ceiling 2m from either       Log On


   



Question 1184838: The ceiling in the hallway 10 m wide is in the shape of a semiellipse and is 9 m
high in the center and 6 m high at the side walls. Find the height of the ceiling
2m from either wall.

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
Let's start by drawing the complete ellipse 10 meters wide.
Then we'll erase the bottom half and draw in the walls and 
floor and the places where we want to find the height at 
(2 meters from the walls).

Since it's:
>>>9 m high in the center and 6 m high at the side wall.<<<
we know that the upper covertex is 3 meters higher than the 
vertices.



a = 5, b = 3, so the equation of the whole ellipse

x%5E2%2Fa%5E2%2By%5E2%2Fb%5E2%22%22=%22%221

x%5E2%2F5%5E2%2By%5E2%2F3%5E2%22%22=%22%221

x%5E2%2F25%5E%22%22%2By%5E2%2F9%5E%22%22%22%22=%22%221

Now we'll erase the bottom half of the ellipse, draw in
the walls.  The floor is 6m below the vertices, so the
walls go down to the points (±5,-6). We'll draw the heights
in green 2m from the walls:



2 meters from the wall is 3 meters from the center so we
first substitute x=3 in the ellipse's equation to see how 
high above the top of the wall the ellipse is there.

x%5E2%2F25%5E%22%22%2By%5E2%2F9%5E%22%22%22%22=%22%221
3%5E2%2F25%5E%22%22%2By%5E2%2F9%5E%22%22%22%22=%22%221
9%5E%22%22%2F25%5E%22%22%2By%5E2%2F9%5E%22%22%22%22=%22%221
Multiply through by 225
81%2B25y%5E2%22%22=%22%22225
25y%5E2%22%22=%22%22144
y%5E2%22%22=%22%22144%2F25
y%22%22=%22%22%22%22+%2B-+12%2F5
We erased the negative value, so
y%22%22=%22%2212%2F5%22%22=%22%222.4

Then we add 6 meters to get the height from the floor.

Answer: 8.4 meters.

Edwin