Engineering Board Exam Reviewer · Parabolas · medium

A parabolic reflector has a rim diameter of 20 cm and is 5 cm deep. How far from the vertex is the focus, in cm?

  1. 10
  2. 2.5
  3. 20
  4. 5

Answer

D. 5

Solution

Place the vertex at the origin: x2=4py with the rim point (10,5): 100=4p(5) p=5 cm.

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