# oblique

Something that is oblique is slanted or not perpendicular. **Oblique
coordinates** are measured on a plane coordinate system whose axes
are not perpendicular. An **oblique angle** is any angle except
a right angle and an **oblique triangle** is any triangle that doesn't contain a right angle (i.e., one in which one
of the internal angles is obtuse). The first reference to 'oblique-angled
triangles' may have been by Thomas Blundevil in his *Exercises* in
1594.