In order to begin to thoroughly analyze what obtuse angle means, we must
proceed fully to clarify the etymological origin of the two words that shape it:
Angle, first of all, is a term that is identified by having Greek origin. It
derives from "ankulos" (twisted), which later derived into the Latin word
"angulus", which already has the meaning of "angle".
Obtuso, secondly, has Latin origin. It comes from "obtusus", which can be
translated as "clumsy", and is the result of the sum of two clearly
differentiated parts: the prefix "ob", which means "against", and the adjective
"tusus", which is synonymous of "beaten".
The angles are geometric shapes that are formed from two
rays originating from the same vertex, or two lines that are on the same surface
and intersect each other. According to its characteristics, we can differentiate
between numerous types of angles.
One of the most common ways of rating angles is according to their width. In
this framework we find the obtuse angles: these are angles
that measure more than 90º and less than 180º. For example:
angles of 92º, 105º, 136º, 161º and 179º.
No less relevant is to determine that an obtuse angle is formed from the
union at a vertex of two rays and that there are several ways to measure
it. However, among the most frequent is to use an angle protractor or to resort
to using the bevel and the square in combination.
According to
DigoPaul,
this means that the obtuse angles have a greater amplitude than the null
angles (which measure 0º), the acute angles (greater
than 0º and less than 90º) and the right angles (90º). On the
other hand, they have a smaller amplitude with respect to the flat
angles (180º) and the perigonal angles (360º).
Other classifications frame the obtuse angles between the oblique
angles (since they are not right) and the convex angles (they
are less than a straight angle).
Different geometric figures have obtuse angles. An example is the obtuse
triangle, which has one obtuse angle and two acute angles. The obtuse
triangles, in turn, are oblique triangles because they do not
have any right angle. Following these classifications, the obtuse triangles can
be isosceles (the obtuse angle is formed by two equal sides,
while the third is greater) or scalene (the three sides measure
differently, even those that make up the obtuse angle).
Also, it should not be forgotten that the obtuse angle becomes a fundamental
pillar of mathematics in general, as does the right angle and the acute angle.
It is important to know that obtuse angles are often confused with socalled
reflex angles. These have the peculiarity that they can measure the same as
those previously mentioned, but they differ in that the reflections are formed
in what is the outer part of the shape.
