Label a Triangle

How to know which side Angle is A - B - C and which side to put a - b - c 

the uppercase letters ABC is the Angles of a Cosine Rule and the lower case abc are its sides 

This is a Cosine Triangle 

 

A right triangle is a special case of the general triangle with one of its angles equal to 90 degrees. A 90-degree angle is called a right angle and that is where the right triangle gets its name.

  

to know the side of this Triangle 

You put where the opposite of the angle A - B - C is to know its side which is lowercase a - b - c 

The Red-letter A - B - C are the Angles of a Cosine Rule 

The Blue arrows pointing from its opposite uppercase letter are its Sides

Link to the Photos NASA