conics problem..?
hi i have two conic problems that i dont know.. plz help me..
dont have to solve this but i just need soem guide… i have hard time understanding the proble,
1.A reflector for a satellite dish is parabolic in cross section, with the receiver at the focus F. The reflector is 1 ft deep and 20 ft wide from rim to rim. How far is the receiver from the vertex of the parabolic reflector?
2.A carpenter wishes to construct an elliptical table top from a sheet of plywood, 4ft by 8ft. he will trace out the ellipse using the thumbtack and string method. what length of string should he use, and how far apart should the tacks be located if the ellipse is to be the largest possible that can be cut out of the plywood sheet?
1. Use y² = 4px (p is the distance from the vertex to the focus)
“The reflector is 1 ft deep and 20 ft wide from rim to rim” means we have a point (1,10)
100 = 4p (p=25)
Ans: 25 ft.
2. Then a = 4 & b = 2.
The length of the string is simply 2a = 8 ft.
a² = b² + c²
c² = 16 – 4 = 12.
The tacks are 2√12 ft apart from each other.
d:
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