A pyramid in Egypt may only look as a triangle in 2-dimensional (2D) form. A triangle is just another basic shape besides the circle and the square. There are a few types of triangles but the first basic thing you should know about the triangle is that it has 3 sides no matter how it is bent or shaped as long as it has three sides and three vertices. Also note that any 3-side polygon has a total interior angle (the angle within/inside of the polygon) of 180 degrees.

Equilateral triangle – An equilateral triangle has all equal sides, meaning to say that all the three sides are the same in length and also angle. As I have foretold, a triangle has a total interior angle of 180 degrees. Thus, the three angles inside the equilateral triangle would be 60 degrees individually.

Isosceles triangle – An isosceles triangle is a triangle where only two sides are equal in length and angle. The unequal length of the triangle, shorter or longer, is usually the base of the triangle. A simple example is, if the two equal sides of the triangle is 30 degrees each, the other angle would be: 180 – 30 – 30 = 120 degrees

Scalene triangle – Scalene triangles are triangles that have all its sides in different lengths and of course, different angles.

A triangle can also be classified by its angle.

Acute-angled triangle – It is a triangle that has all three acute angles. An acute angle is an angle less than 90 degrees. An example would be the equilateral triangle where all the three angles are 60 degrees, which is obviously less than 90 degrees.

Right-angled triangle – It is a triangle where one of its angles is a right angle. A right angle is always 90 degrees! That’s something you should always remember.

Obtuse-angled triangle – It is a triangle where one of its angles is an obtuse angle. An obtuse angle is an angle greater than 90 degrees but less than 180 degrees. An example of this type of triangle is the isosceles triangle as shown in the example above. However, note that not all isosceles triangles can be categorized as obtuse-angled triangles.

*Area of a triangle can be calculated by using the formula: 1/2 x base x height

For more complex problems, the Pythagoras' Theorem can be used: A(squared) + B(squared) = C(squared)

where C is the hypotenuse (the longest length) of the triangle.

A triangle is a very interesting shape if you know all its characteristics and it would be very easy to solve any solutions related to lines and angles of a triangle. Also remember that the total exterior angle of the triangle or any other polygons is 360 degrees.