Chapters

## Perimeter of a Triangle

The perimeter of a triangle equals the sum of the length of its three sides.

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1st lesson free!  4.9 (26 reviews)
Intasar
£36
/h
1st lesson free!  5 (17 reviews)
Matthew
£25
/h
1st lesson free!  4.9 (13 reviews)
Paolo
£25
/h
1st lesson free!  4.9 (7 reviews)
Dr. Kritaphat
£49
/h
1st lesson free!  5 (28 reviews)
Ayush
£60
/h
1st lesson free!  4.9 (9 reviews)
Petar
£27
/h
1st lesson free!  5 (14 reviews)
Farooq
£40
/h
1st lesson free!  5 (9 reviews)
Tom
£22
/h

## 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 around 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  Need a Maths teacher?

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Emma

I am passionate about travelling and currently live and work in Paris. I like to spend my time reading, gardening, running, learning languages and exploring new places.