  We introduce a bulging triangle like the generalization of the Reuleaux
triangle. We may be able to propose various ways to bulge a triangle, but this
paper presents the way so that its vertices are the same as them of the
original triangle. We find some properties and theorems of our bulging
triangles. In particular, we investigate, via calculus, whether basic facts
such as triangle inequalities and Pythagorean theorem hold for bulging
triangles.
