Final answer:
There are 165 triangles that can be formed using the vertices of a regular 11-sided polygon.
Step-by-step explanation:
A regular 11-sided polygon is called an hendecagon. To form a triangle using the vertices of the hendecagon, we need to choose 3 out of the 11 vertices. The number of ways to choose 3 vertices out of 11 is given by the combination formula:
C(11, 3) = 11! / (3! * (11-3)!) = 165
Therefore, it is possible to form 165 triangles using the vertices of the 11-sided polygon.