+0  
 
0
1802
1
avatar

A circle is drawn that intersects all three sides of triangle PQR as shown below. Prove that if AB = CD = EF, then the center of the circle is the incenter of triangle PQR.
 

 Jan 17, 2017
 #1
avatar+129839 
0

A circle is drawn that intersects all three sides of triangle PQR as shown below. Prove that if AB = CD = EF, then the center of the circle is the incenter of triangle PQR.

 

 

 

Take O as the center of the circle

Draw OG, OH, OI   perpendicular  to  AB, CD  and EF  respectively

And, by Euclid.....equal chords are equal distances from the center of  a circle

So GO = HO and OQ is common

So triangles QOG  and QOH are congruent right triangles by HL

So < GQO  = < HQO

By similar reasoning, triangles ROH and ROI  are congruent right triangles by HL

So < HRO  = < IRO

And once more, triangles POI and POG  are congruent right triangles by HL

So < IPO  = < GPO

 

Therefore......since QO, RO and PO  are angle bisectors of triangle PQR that meet at O, then O is the triangle incenter.....but O is also the center of the circle

 

 

cool cool cool

 Jan 18, 2017

2 Online Users

avatar