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Area and Perimeter of Plane Figure

  • Perimeter is the length of the boundary of a closed figure.
  • The perimeter of a polygon is the sum of the lengths of all its sides.

In case of a triangle ABC, with sides of lengths a, b and c units:

Perimeter of ABC = AB + BC + AC = a + b + c

  • The semi-perimeter of a triangle is half the perimeter of the triangle.

The semi-perimeter (s) of a triangle with sides a, b and c is.

  • The semi-perimeter of a triangle is used for calculating its area when the length of altitude is not known.
  • Area of a triangle:
    • Area of a triangle =
    • All the congruent triangles are equal in area, but the triangles having equal areas may or may not be congruent.

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