A triangle is a type of polygon, which has three sides, and the two sides are joined end to end is called the vertex of the triangle

Triangle is a closed two-dimensional shape. It is a three-sided polygon. All sides are made of straight lines. The point where two straight lines join is the vertex.

Explanation: Perimeter of a triangle = a + b + c
Area of a triangle = \$(1/2) \times h \times b\$