Triangle with all angles less than ninety?

In plane geometry, all triangles have the sum of the angles to be 180 degrees. So There are many triangles with all the angles less than 90. ( if one angle is more than 90 degrees, then its called 'obtuse' , if all the angles are less than 90, then its called 'Acute' ).

Two types of triangles with angles less than 90 degrees are Equalaterial and Isocoles. ( Equalaterial have two equal angles, Isocoles have three equal angles, all 60 degress ).

You can think in terms of sets:

The subset of Triangles is Acute,

The subset of Acute Triangles is Equalateral,

The subset of Equalateral Triangles is Isocoles.

{Triangles{Obtuse|Acute{Equlaterial{Isocoles