Area and Perimeter of a Triangle
Perimeter of a Triangle
The perimeter of a triangle equals the sum of the length of its three sides.
| Equilateral Triangle | Isosceles Triangle | Scalene Triangle |
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Area of a Triangle
The area of a triangle is equal to half its base times its height.
The height of a triangle is each of the perpendicular lines drawn from one vertex to the opposite side (or its extension).
Example
Find the area of the triangle:
Area of an Equilateral Triangle
Example
Calculate the area of an equilateral triangle with a side of 10 cm.
Area of a Right Triangle
The area of a right triangle equals half the product of the legs.
Example
Calculate the area of the right triangle with legs measuring 3 and 4 cm.
Semiperimeter
The semiperimeter of a triangle equals half the sum of its sides.
It is denoted with the letter s.
Heron's Formula
Heron's formula is used to find the area of a triangle knowing the length of all three sides.
Example
Find the area of the triangle with sides measuring 3, 4 and 5 cm.
Circumscribed Circle in a Triangle
R = radius of the circumscribed circle.
Inscribed Circle in a Triangle
r = radius of the inscribed circle.
s = semiperimeter
Knowing the Lengths of Two Sides and the Angle between them
