Perimeter and area of a triangle

The perimeter of a triangle is the sum of the length of its three sides, whether they are equal or not.

Equilateral Isosceles Scalene
image/svg+xml l P=3·l image/svg+xml l P=2·l+b l b image/svg+xml a P=a+b+c c b

The area of a triangle is equal to the basis multiplied by the height divided by $2$.

image/svg+xml

$$A=\dfrac{b \cdot h}{2}$$

Semiperimeter of a triangle

The semiperimeter of a triangle is equal to the sum of its sides divided by $2$.

It is normally denoted with the letter p (in lower case) and we express it as:

$$p= \dfrac{a+b+c}{2}$$

Practice exercises