Inscribed circle in the triangle

Consider the above diagram.In summary, The point I is the center of the inscribed circle in a triangle. A line AI intersects segment BC at point D. The angle bisector of AD intersects lines BI and CI at points P and Q respectively. It is required to prove that the heights of triangle PQD intersect at point I. A diagram is provided and it is stated that the orthocenter of PDQ is I. To prove this, it is sufficient to show that angle BH_QD is a right angle.
  • #1
Mathick
23
0
In the triangle a point \(\displaystyle I\) is a centre of inscribed circle. A line \(\displaystyle AI\) meets a segment \(\displaystyle BC\) in a point \(\displaystyle D\). A bisector of \(\displaystyle AD\) meets lines \(\displaystyle BI\) and \(\displaystyle CI\) respectively in a points \(\displaystyle P\) and \(\displaystyle Q\). Prove that heights of triangle \(\displaystyle PQD\) meet in the point \(\displaystyle I\).

I've tried to show that sides of triangle \(\displaystyle PQD\) are parallel to sides of triangle \(\displaystyle ABC\) but it didn't work out. That's why I ask you for help.
 
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  • #2
Can you provide a diagram?
 
  • #3
I am convinced the OP has posted a true statement. I can't prove it, but hope someone here can. Here's a diagram.

1hug6x.png


Give a triangle ABC, let I be the incenter of the triangle (the intersection of the angle bisectors at A, B and C). Let D be the intersection of AI with BC and line L the perpendicular bisector of AD ($H_D$ is the midpoint of AD). Let P be the intersection of CI with L and Q the intersection of BI with L. Then the orthocenter of PDQ is I.

Clearly, if $H_Q$ is the intersection of BI with DP, it is sufficient to show angle $BH_QD$ is a right angle.
 

1. What is an inscribed circle in a triangle?

An inscribed circle in a triangle is a circle that is tangent to all three sides of the triangle. This means that the circle touches all three sides of the triangle at exactly one point.

2. What is the center of an inscribed circle in a triangle?

The center of an inscribed circle in a triangle is the point where the three angle bisectors of the triangle intersect. This point is also known as the incenter of the triangle.

3. How is the radius of an inscribed circle in a triangle calculated?

The radius of an inscribed circle in a triangle can be calculated using the formula r = A / s, where A is the area of the triangle and s is the semi-perimeter (half of the perimeter) of the triangle.

4. What is the relationship between the sides of a triangle and the radius of an inscribed circle?

The radius of an inscribed circle is inversely proportional to the sides of the triangle. This means that as the sides of the triangle get longer, the radius of the inscribed circle gets smaller, and vice versa.

5. How is the inscribed circle used in geometry?

The inscribed circle is useful in geometry for finding the incenter of a triangle, as well as for solving various problems involving tangency and angle bisectors. It is also used in constructions for creating circles that are tangent to three given lines or circles.

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