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# Triangles

Triangle plays a very important role in the field of Geometry. Triangle is a geometrical shape which consists of three sides and three angles. The sum of the angles in a triangle is 180 degree. The sides of the triangle may or may not be the same. Depending on this the Triangles are classified as: Equilateral Triangle, Isosceles Triangle and Scalene Triangle.

If all the sides of the triangle are equal then it is an Equilateral Triangle. In a triangle if the three sides are equal, then automatically the three angles will be equal. Here each angle will be of 60 degree as 3x = 180, so ‘x’ will be equal to 60 degree, here ‘x’ is the angle.

If two sides of the triangle are equal then it is a Isosceles Triangle. In a triangle if the two sides are equal, then automatically the two angles will be equal. In a triangle, if no side is equal then the triangle is called as Scalene Triangle. The angles in a scalene triangle are all different.

If we are having a triangle in which all angles are less than ninety degree then this type of articles are called as Acute Angle. If we are having a triangle in which one angle will be of ninety degree then this type of triangle is called as Right Angle triangle. If we are having a triangle in which one side is greater than ninety degree then this type of triangle are called as Obtuse Triangle.

If we are having a right angle triangle but opposite side of the angles are equal then the other angle will be of 45 degree. This type of triangle is called as right angle isosceles triangle. If we are having a triangle with two angles as 45 and 100 and our task is to find the third angle. We can find it very easily as we know that sum of all the angles of triangle is 180. So the third angle can be found as,
45 + 100 + x = 180
145 + x = 180
x = 180 - 145
x = 35
The third angle is 35 degree.

## Triangle Sum Theorem

Triangle plays a very important role in the field of Geometry. Triangle is a geometrical shape which consists of three sides and three angles. The sum of the angles in a triangle is 180 degree. This is proved by the theorem given below known as the 'Triangle Sum Theorem'

Statement:
Sum of all the angles in a triangle is equals to 180 degrees.

## Classifying Triangles by sides or Angles

We know that a triangle is a Polygon which has three sides, 3 angles & 3 vertices. Now the Triangles can be classified further on the basis of the length of their sides & also on the basis of their ...Read More

## The Triangle Defined

A line segment is a part of a line with two fixed points. It can be drawn by joining any two points on a plane. It has only length. Remember that two points always form a line whichever may be the direction.
On the other hand, if 3 or more points are marked on a plane, they may or may not lie in the same line. When 3 or more points lie in the same line, they are ca...Read More

## Congruent Triangles

Congruent Triangles are basically those Similar Triangles which are same in size and angle. But these triangles are flipped. According to congruent triangles definition, triangles are congruent only when all interior an...Read More

## Exterior Angle of a Triangle

An exterior angle of a triangle is defined when out of three sides one side is extended outside the triangle, exterior angles of a triangle is always bigger than the interior angles or we can say that the sum of two interior angles of a triangle is equal to the exterior angle of triangle. Three corners of a triangle are known as vertices. An exterior angle o...Read More

## Special Features of Isosceles Triangles

Triangles are the polygons with three sides. We say that the triangle is the closed figure with three sides. Now we need to know that the Triangles are classified as per the measure of their lengths ...Read More

## Angle Sum of a Triangle

We know that the sum of angles in a triangle is always fixed, which is equal to 180 degrees. As we know that the  angle sum of a triangle is always 180 degrees, thus if any two angles of the triangle is known then we can find the  third angle of the triangle by adding the two given angles and then by subtracting the sum of the  two angles by 180 degrees. If we ha...Read More

## Triangle Inequalities

In a triangle there are three sides, than any one side of a triangle is always smaller than the sum of all the two other sides is the inequalities of triangle. In just opposite case, if any one side of a triangle is a...Read More

## Special names for sides and angles

Each Geometry angles and each geometry side has its own name, which is called as a Special name for sides and angles. Now we discuss each and every Special name for sides and angles:
Altitude side – alti...Read More