# Homework Help: Triangle on a Sphere Question Interpretation

1. Sep 17, 2012

### tainted

1. The problem statement, all variables and given/known data
Consider a tiling of the unit sphere in $\mathbb R^3$ by equilateral triangles so that the triangles
meet full edge to full edge (and vertex to vertex). Suppose n such triangles meet an one
vertex. Show that the only possibilities for n are
$n=3$, $n = 4$, or $n=5$

2. Relevant equations

3. The attempt at a solution
I guess the main thing I need help with is interpretation of the question.

Thank you

2. Sep 17, 2012

### HallsofIvy

A (flat) triangle won't fit on the surface of a sphere. Do you mean spherical triangles?

3. Sep 17, 2012

### Dick

Hint: there's a relation between the angles of a triangle and it's area. Figure out the area of a triangle if n of them share a vertex. How many will fit on a sphere? If you think about there is also a easy correspondence between these and some of the platonic solids.