Proving Perpendicularity of FE & AB in a Semicircle

  • Thread starter Saad
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In summary, the problem asks to prove that the extension of FE is perpendicular to AB, given that AB is the diameter of a semicircle and points C and D are on the arc of the semicircle. This can be proven using analytical geometry by considering the right triangles ACB and ADB with right angles at C and D.
  • #1
Saad
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AB is the diameter of a semicircle. Points C and D are ANY two points on the arc of the semicircle. AD and BC intersect at E. AC and BD are extended to meet at F. Prove that FE extended is perpendicular to AB.

I need any help possible because i have no idea of how to solve this proof problem! pleasezzzzzzzzzzzzz
 
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  • #2
The assertion is fairly easy to prove if you rephrase it in the terms of analytical geometry.
It looks difficult to prove it by "classical" means (i.e. identifying congruent triangles and suchlike)
 
  • #3
Use the fact that triangles ACB and ADB are right triangles with right angle at C and D.
 

1. What is the definition of perpendicularity?

Perpendicularity is a geometric property where two lines or segments intersect at a 90-degree angle, forming a right angle.

2. How can I prove that FE and AB are perpendicular in a semicircle?

To prove perpendicularity in a semicircle, we can use the theorem that states that a line drawn from the center of a circle to any point on the circle is perpendicular to the tangent line at that point. Therefore, we can draw a line from the center of the semicircle to point E on FE and another line from the center to point B on AB. If these lines are perpendicular, then FE and AB are also perpendicular.

3. Can I use the Pythagorean theorem to prove perpendicularity in a semicircle?

Yes, the Pythagorean theorem can also be used to prove perpendicularity in a semicircle. If we have a right triangle formed by the center of the semicircle, point E, and point B, we can use the theorem to show that the square of the hypotenuse (the line connecting E and B) is equal to the sum of the squares of the other two sides (the lines connecting E and the center, and B and the center).

4. Are there any other methods to prove perpendicularity in a semicircle?

Yes, there are other methods that can be used to prove perpendicularity in a semicircle, such as using the inscribed angle theorem or the congruent triangles theorem. However, the methods described above (using the tangent theorem or the Pythagorean theorem) are the most commonly used and straightforward.

5. Why is it important to prove perpendicularity in a semicircle?

Proving perpendicularity in a semicircle is important because it allows us to accurately measure and construct angles and shapes within the semicircle. It is also a fundamental concept in geometry and is used to solve more complex problems and theorems.

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