An obtuse triangle is a triangle through one inner angle measure greater than 90 degrees. In geometry, triangles are considered as 2D closed numbers with 3 sides of the exact same or various lengths and also three angles v the same or different measurements. Based on the length, angles, and also properties, over there are 6 kinds that triangles that we discover in geometry i.e. Scalene triangle, ideal triangle, acute triangle, obtuse triangle, isosceles triangle, and equilateral triangle.

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If among the internal angles the the triangle is much more than 90°, climate the triangle is called the obtuse-angled triangle. Let's learn much more about obtuse triangles, their properties, the formulas required, and solve a few examples to understand the concept better.

1.What Is one Obtuse Triangle?
2.Obtuse Angled Triangle Formula
3.Obtuse Angled Triangle Properties
4.FAQs top top Obtuse Triangles

What Is an Obtuse Triangle?

An obtuse-angled triangle or obtuse triangle is a form of triangle whose one of the vertex angle is bigger 보다 90°. One obtuse-angled triangle has actually one of its vertex angle as obtuse and also other angle as acute angle i.e. If among the angle measure an ext than 90°, climate the sum of the various other two angles is much less than 90°. The next opposite come the obtuse angle is taken into consideration the longest. Because that example, in a triangle ABC, three sides the a triangle measure a, b, and c, c being the longest next of the triangle together it is the opposite side to the obtuse angle. Hence, the triangle is one obtuse-angled triangle whereby a2 + b2 2

An obtuse-angled triangle deserve to be a scalene triangle or isosceles triangle yet will never ever be equilateral since an it is provided triangle has actually equal sides and also angles where each angle steps 60°. Similarly, a triangle cannot be both one obtuse and a right-angled triangle because the right triangle has one angle of 90° and the other two angles space acute. Therefore, a right-angle triangle cannot be an obtuse triangle and also vice versa. Centroid and incenter lie in ~ the obtuse-angled triangle if circumcenter and orthocenter lie outside the triangle.

The triangle listed below has one angle higher than 90°. Therefore, it is dubbed an obtuse-angled triangle or merely an obtuse triangle.


Obtuse Angled Triangle Formula

There are separate formulas to calculate the perimeter and the area of one obtuse triangle. Let's discover each that the recipe in detail.

Obtuse Triangle Perimeter

The perimeter of one obtuse triangle is the amount of the measures of all its sides. Hence, the formula for the perimeter of one obtuse-angled triangle is:

Perimeter that obtuse angled triangle = (a + b + c) units.

Area the Obtuse Triangle

To uncover the area of one obtuse triangle, a perpendicular line is created outside of the triangle whereby the height is obtained. Due to the fact that an obtuse triangle has a worth of one angle more than 90°. As soon as the height is obtained, us can discover the area of an obtuse triangle by using the formula stated below.

In the given obtuse triangle ΔABC, we understand that a triangle has actually three altitudes native the three vertices to the the opposite sides. The altitude or the height from the acute angle of an obtuse triangle lies outside the triangle. We extend the base together shown and determine the height of the obtuse triangle


Area that ΔABC = 1/2 × h × b whereby BC is the base, and h is the height of the triangle.

Area of one Obtuse-Angled Triangle = 1/2 × basic × Height

Obtuse Triangle Area through Heron's Formula

The area of one obtuse triangle can also be found by utilizing Heron's formula. Take into consideration the triangle ΔABC v the length of the sides a, b, and also c.

Heron's formula to uncover the area of one obtuse triangle is: \(\sqrt s(s - a)(s - b)(s - c)\), where, (a + b + c) is the perimeter that the triangle and S is the semi-perimeter i m sorry is given by (s): = (a + b + c)/2

Properties that Obtuse-Angled Triangles

Each triangle has its own properties that specify them. An obtuse triangle has four different properties. Let's watch what castle are:

Property 1: The longest side of a triangle is the next opposite to the obtuse angle. Take into consideration the ΔABC, side BC is the longest side which is opposite come the obtuse angle ∠A. See the image listed below for reference.


Property 2: A triangle deserve to only have actually one obtuse angle. We understand that the angles of a triangle amount up to 180°. Take into consideration the obtuse triangle shown below. We have the right to observe that among the angle measures better than 90°, making the an obtuse angle. Because that instance, if one of the angle is 91°, the amount of the other two angles will be 89°. Hence, a triangle cannot have two obtuse angles due to the fact that the sum of all the angles cannot exceed 180 degrees. Observe the image given below to understand the exact same with an illustration.


Property 3: The sum of the other two angles in an obtuse triangle is always smaller 보다 90°. We just learned that as soon as one of the angle is one obtuse angle, the various other two angles add up to much less than 90°.


In the above triangle, ∠1 > 90°. We understand that by angle amount property, the sum of the angle of a triangle is 180°. Therefore, ∠1 + ∠2 + ∠3 = 180° and ∠1 > 90°

Subtracting the over two, us have, ∠2 + ∠3 As seen in the photo below:


Circumcenter (H), the median suggest from every the triangle vertices, lies exterior in an obtuse triangle. As seen in the photo below:


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Example 2: find the height of the given obtuse-angled triangle who area = 60 in2 and base = 8 in.



Area of an obtuse-angled triangle = 1/2 × basic × height. Therefore, the height of the obtuse triangle deserve to be calculation by:

Height = (2 × Area)/base

Substituting the values, we get:

Height = (2 × 60)/8 = 15 inches

Therefore, the height of the provided obtuse triangle is 15 inches.

Example 3: can sides measure up 3 inches, 4 inches, and also 6 inches type an obtuse triangle?


The political parties of one obtuse triangle should satisfy the condition that the sum of the squares of any two sides is lesser than the square that the third side.

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We know that

a = 3 in

b = 4 in

c = 6 in

Taking the squares the the sides, we get: a2 = 9, b2 = 16, and also c2 = 36

We recognize that, a2 + b2 2

36 > (9 + 16)

The offered measures can kind the political parties of an obtuse triangle. Therefore, 3 inches, 4 inches, and 6 inches deserve to be the political parties of an obtuse triangle.