MHB Inscribed circle in the triangle

AI Thread Summary
The discussion focuses on proving that the heights of triangle PQD intersect at the incenter I of triangle ABC. The participants explore the relationship between triangle sides and their bisectors, specifically how the line AI intersects segment BC at point D. A diagram is requested to clarify the geometric relationships, and one participant provides a detailed construction involving perpendicular bisectors and intersections. The proof hinges on demonstrating that angle BH_QD is a right angle, confirming that the orthocenter of triangle PDQ is indeed point I. This geometric configuration illustrates the properties of inscribed circles and triangle centers.
Mathick
Messages
23
Reaction score
0
In the triangle a point $$I$$ is a centre of inscribed circle. A line $$AI$$ meets a segment $$BC$$ in a point $$D$$. A bisector of $$AD$$ meets lines $$BI$$ and $$CI$$ respectively in a points $$P$$ and $$Q$$. Prove that heights of triangle $$PQD$$ meet in the point $$I$$.

I've tried to show that sides of triangle $$PQD$$ are parallel to sides of triangle $$ABC$$ but it didn't work out. That's why I ask you for help.
 
Mathematics news on Phys.org
Can you provide a diagram?
 
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.
 
Seemingly by some mathematical coincidence, a hexagon of sides 2,2,7,7, 11, and 11 can be inscribed in a circle of radius 7. The other day I saw a math problem on line, which they said came from a Polish Olympiad, where you compute the length x of the 3rd side which is the same as the radius, so that the sides of length 2,x, and 11 are inscribed on the arc of a semi-circle. The law of cosines applied twice gives the answer for x of exactly 7, but the arithmetic is so complex that the...
Thread 'Video on imaginary numbers and some queries'
Hi, I was watching the following video. I found some points confusing. Could you please help me to understand the gaps? Thanks, in advance! Question 1: Around 4:22, the video says the following. So for those mathematicians, negative numbers didn't exist. You could subtract, that is find the difference between two positive quantities, but you couldn't have a negative answer or negative coefficients. Mathematicians were so averse to negative numbers that there was no single quadratic...
Thread 'Unit Circle Double Angle Derivations'
Here I made a terrible mistake of assuming this to be an equilateral triangle and set 2sinx=1 => x=pi/6. Although this did derive the double angle formulas it also led into a terrible mess trying to find all the combinations of sides. I must have been tired and just assumed 6x=180 and 2sinx=1. By that time, I was so mindset that I nearly scolded a person for even saying 90-x. I wonder if this is a case of biased observation that seeks to dis credit me like Jesus of Nazareth since in reality...
Back
Top