Track / Stage 4 / 201 of 340 #461 of 1964
Problem 461
AMC 12 late, AIME early Geometry Difficulty 4.8 Find the answer
Ex. 2. Find the radius of the circle inscribed in a triangle with sides 9,10,11.
将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。
(Note: The note at the end is not part of the translation but is provided to clarify the instruction.)
A number or a short expression. Spacing and $ signs are ignored.
Official solution
Source: NuminaMath-1.5,
licensed Apache-2.0.
Statement and solution reproduced as published; topic, difficulty and ordering added
by this site.