Obtuse Angle

                                                                                                          
In this article we shall learn about What is an Obtuse Angle? And also about Obtuse Scalene Triangle. Before studying about obtuse angle let us learn the definition of ‘angle’. In terms of geometry, an angle is defined as a measure between the circular arc and its radius and it’s shape is formed by two rays called as the sides (arms) of the angle and it shares an end point which is common to the two rays i.e., vertex of the angle. The units to measure an angle are degrees in sexagesimal system, radians in circular system and grades in centismal system.

We have various types of angles such like acute angles, right angles, obtuse angles, supplementary angles, straight angle, reflex angles etc. There are few properties which are listed below:

•    The measure of it can be positive or negative.
•    The measure of it can exceed 360°.
•    When we have two angles such as 30° and 390° where 390° = 360° + 30° where it means that the two terminal sides 30° and 390° belongs to same plane. Hence these two angles are called Coterminal angles.
•    It is expressed in terms of degrees and radians.

So far, we have learnt about definition of angle and its properties, now let us define obtuse angle?
It is defined as an angle whose measure will be greater than 90 degrees but less than 180 degrees. If the measure of this is not between 90 degrees to 180 degrees is not considered as an obtuse angle. Even if the measure is exactly 90 degrees is called as a right angle but not an obtuse. In other words, it is defined as the swipe between the quarter and the half rotation of a circle whose measure varies from 90 degrees to 180 degrees.

Now let us see about Obtuse Scalene Triangle. Firstly, Scalene Triangle is defined as a triangle, whose all sides are unequal and all angles are unequal. Where as an obtuse scalene triangle definition is similar to a scalene triangle where one of its angle is greater than 90°. An obtuse scalene triangle has one obtuse angle and two acute angles, where the two acute angles may be equal or unequal. If the two acute angles are equal then it is known as an obtuse isosceles triangle. There are few facts about scalene triangle such as

•    All interior angles are different.
•    The side which is opposite to the smallest angle will be the shortest side.
•    Similarly, the side which is opposite to the largest angle will be the longest side.

In order to find the area of an obtuse triangle the best formula to use is “heron’s formula”.

According to heron’s formula, the area A of a triangle whose sides are a, b, c is as follows:

A = √s(s-a)(s-b)(s-c), where a, b, c are sides of triangle and ‘s’ is the semi perimeter of the triangle. i.e., S = (a + b + c) / 2.