## Geometry: Common Core (15th Edition)

A triangle that is a right triangle cannot be obtuse. A right triangle already has a right angle that equals $90^{\circ}$. The interior angles of a right triangle can only add up to exactly $180^{\circ}$; therefore, the other two angles can add up to only $90^{\circ}$, so there cannot be an obtuse angle in this triangle. Statements I and II contradict each other.