Hyperbolic geometry or hypercycle, then the triangle has no circumscribed circle. As in spherical and elliptical geometry, in hyperbolic geometry if two triangles are similar, they must be congruent. A special polygon in hyperbolic geometry is the regular apeirogon, a uniform polygon with an infinite number of sides. In Euclidean geometry, the only way to construct such a polygon is to make the side lengths tend to zero and the apeirogon is indistinguishable from a circle, or make the interior angles tend to 180 degrees and the apeirogon approaches a straight line. However, in hyperbolic geometry, a regular apeirogon has sides of
Blues scale major scale featuring a flat third and seventh degrees (in effect substitutions from Dorian mode) which, "alternating with the normal third and seventh scale degrees are used to create the blues inflection. These 'blue notes' represent the influence of African scales on this music." \override Score.TimeSignature #'stencil = ##f \relative c' { </score> A different and non-formal way of playing the scale is by the use of quarter tones, added to the 3rd and 7th degrees of the minor blues scale. For example, the A minor blues scale with quarter tones is A–B–C–D–E–F–G, where is a half sharp. Also, the