What is the Law of Sines?

1 Answer
Jan 30, 2015

First of all it is useful to say the notation in a triangle:

Opposite at the side #a# the angle is called #A#,
Opposite at the side #b# the angle is called #B#,
Opposite at the side #c# the angle is called #C#.

So, the Sinus Law can be written:

#a/sinA=b/sinB=c/sinC#.

This Law is useful in all the cases SSA and NOT in the case SAS, in which the Law of Cosinus has to be used.

E.G.: we know #a,b,A#, then:

#sinB=sinA*b/a# and so #B# is known;

#C=180°-A-B# and so #C# is known;

#c=sinC/sinB*b#