Track / Stage 4 / 168 of 340 #428 of 2000

Problem 428

AMC 12 late, AIME early

Combinatorics Difficulty 4.9 Find the answer

6. The set of points on the complex plane corresponding to the roots of the equation $x^{10}=1$ is $M$ . Among the triangles formed by the points in $M$ , the number of different right-angled triangles is
A. 120
B. 80
C. 40
D. 680

Your answer

Official solution

6. $\mathrm{C}$

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.