Perimeter of a Scalene Triangle
If you know the length of the three sides, it’s easy to calculate its perimeter using the following formula:
If you know two sides of the triangle and the angle they form you can solve for the missing side using the Law of Cosines (Cosine Rule):
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Note. Courtesy of the author: José María Pareja Marcano. Chemist. Seville, Spain.
Consider a given triangle:
Let be a scalene triangle of known sides, these being a=2 cm, b=4 cm and c=3 cm.
What is its perimeter? This will be calculated as the sum of its three sides.
So, the perimeter is 9 cm.
What is its perimeter?
In this triangle we only know two sides (a=4 cm y c=6 cm) and the angle they form (B=85°). First we have to find the length of side b.
For this we use the Law of Cosines:
So, we get the side b=6.92 cm.
Now we can calculate the perimeter by adding the three sides of the triangle:
The perimeter of the triangle is 16.92 cm.
AUTHOR: Bernat Requena Serra