SOLUTION: A parabolic eavesdropping device is used by an intelligence agent to record terrorist conversations. The parabolic surface measures 120 cm in diameter at the top and is 20 cm deep

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: A parabolic eavesdropping device is used by an intelligence agent to record terrorist conversations. The parabolic surface measures 120 cm in diameter at the top and is 20 cm deep       Log On


   

Question 1160971: A parabolic eavesdropping device is used by an intelligence agent to record terrorist conversations. The parabolic surface measures 120 cm in diameter at the top and is 20 cm deep at its center. How far from the vertex should the microphone be​ located?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
---------------------------------
The parabolic surface measures 120 cm in diameter at the top and is 20 cm deep at its center. How far from the vertex should the microphone be​ located?
------------------------------


Putting vertex at (0,0) and two points (-60,20) and (60,20),
y=ax%5E2
20%2Aa%2A60%5E2
a=1%2F180
-
180y=x%5E2

Focus is d cm from vertex.
4d=180
d=180%2F4
highlight%28d=45%29cm from vertex