How do you find the total perimeter of a triangle from 2 sides?

Answer by  algebraguru (28)

You can't with only the lengths of two sides. The perimeter of a triangle is the sum of the lengths of all three sides. You only know that the perimeter is larger than the sum of those two lengths and smaller than twice the sum of the two lengths.

Answer by  Joven (163)

Just having the 2 sides of the triangle is not sufficient information, you will also need to know the angle between those two sides. With the angle you can use the law of cosines to determine the other side and then add up all 3 sides to get the perimeter. If the angle is 90, you can use Pythagorean theorem.