Scalene, equilateral triangle and valid triangle?

Question

how to guess the triangle is valid using lengths/ angles ?

Answer 1

A quick test to check if the given lengths of the sides are valid signs of a triangle:

If "a", "b" and "c" are the given sides, then for a triangle to be valid, the sum of any two sides must be greater than the third side.

Mathematically,

a + b > c

OR

a + c > b

OR

b + c > a

Other definitions:

Scalene triangle -- a triangle where the lengths of all the three sides are different from each other. The angles are also not equal to each other.

Equilateral triangle -- all the sides have the same lengths and the angles measure 60 degrees each.

Isosceles triangle -- two of the sides have the same lengths and the angles adjacent to these equal sides are also equal.

Right triangle -- one of the angles is equal to 90 degrees and the side opposite the 90-deg angle is called the hypotenuse, which is also the longest side in a right triangle.

Hope the above helps.