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 so-called 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.