Help with Parabola Question by Monday

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SUMMARY

The discussion centers on solving a geometry problem involving parabolas, specifically relating to the properties of triangles formed by points on the parabola. The user successfully demonstrated that line FN is perpendicular to line PA, utilizing the slopes of these lines. The key property of parabolas discussed is that the lengths of segments FP and PN are equal, which is crucial for proving the congruence of triangles PAF and PAN. The conversation emphasizes the application of the law of reflection in understanding the path of light as it interacts with the parabola.

PREREQUISITES
  • Understanding of basic geometry concepts, particularly triangles and angles.
  • Familiarity with the properties of parabolas, including the definition and reflective properties.
  • Knowledge of slopes and gradients in coordinate geometry.
  • Basic principles of the law of reflection as it applies to mirrors.
NEXT STEPS
  • Study the properties of parabolas in-depth, focusing on their reflective characteristics.
  • Learn about congruent triangles and the criteria for triangle congruence.
  • Explore the law of reflection and its applications in optics.
  • Practice solving geometry problems involving slopes and angles to reinforce understanding.
USEFUL FOR

This discussion is beneficial for students studying geometry, particularly those focusing on parabolas and their properties, as well as educators seeking to clarify concepts related to reflection and triangle congruence.

PotatoSalad
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Can somebody please help me with this question. I keep thinking I have made some progress on it and it turns out to be totally useless work. Spent almost 2 days struggling over this problem and 2 others and they have to be done for Monday. I have scanned in the question below.

http://img168.imageshack.us/img168/241/prob6ud2.jpg

If anyone can help me with this it will be greatly greatly appreciated.
 
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considering the gradients of the lines means their slopes. that is, using the slopes show that FN is at right angles with PA.

then you can use a property of a parobala that will let you conclude that triangle PAF is the same as triangle PAN. and so are the corresponding angles.

then you must relate this conclusion to the actual path the ray of light takes when it bounces off the parabola. that is, consider the law of reflection for the flat mirror AP.
 
abode_x said:
considering the gradients of the lines means their slopes. that is, using the slopes show that FN is at right angles with PA.

then you can use a property of a parobala that will let you conclude that triangle PAF is the same as triangle PAN. and so are the corresponding angles.

then you must relate this conclusion to the actual path the ray of light takes when it bounces off the parabola. that is, consider the law of reflection for the flat mirror AP.

Ok thanks adobe. I have managed to prove that the line FN and PA are perpendicular.

What is the property of the parabola that you mention in the 2nd paragraph? I have barely done any work on this type of stuff in the past so I am not sure about it. Is it that the line FP is always the same length as PN? Or is that not true?

Thanks again.
 
"Is it that the line FP is always the same length as PN? Or is that not true?"

i think that's it. (look at definition of a parabola)
 
Ok I've got it, it just clicked in my brain this morning. Thanks a lot adobe.
 

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