Difference between revisions of "1998 IMO Problems/Problem 5"

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==Problem==
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Let I be the incenter of triangle ABC. Let the incircle of ABC touch the sides
 
Let I be the incenter of triangle ABC. Let the incircle of ABC touch the sides
 
BC, CA, and AB at K, L, and M , respectively. The line through B parallel
 
BC, CA, and AB at K, L, and M , respectively. The line through B parallel
 
to M K meets the lines LM and LK at R and S, respectively. Prove that angle
 
to M K meets the lines LM and LK at R and S, respectively. Prove that angle
 
RIS is acute.
 
RIS is acute.
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==Solution==
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{{solution}}
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==See Also==
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{{IMO box|year=1998|num-b=4|num-a=6}}

Revision as of 22:50, 18 November 2023

Problem

Let I be the incenter of triangle ABC. Let the incircle of ABC touch the sides BC, CA, and AB at K, L, and M , respectively. The line through B parallel to M K meets the lines LM and LK at R and S, respectively. Prove that angle RIS is acute.

Solution

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See Also

1998 IMO (Problems) • Resources
Preceded by
Problem 4
1 2 3 4 5 6 Followed by
Problem 6
All IMO Problems and Solutions