The Law of Sines states that each side of a triangle is proportional to the
sine of the opposite angle. It looks like this:
The law of sines can be used when two angles and a side of a triangle are known.
Consider the following problem, in which we have two angles and the side
opposite one of them:
A = 35o,
B = 49o, and
a = 7. The first part
we calculate is the third angle,
C.
C = 180o -35o -49o = 96o. Then, using the Law of Sines,
b and
c can be calculated.
=
=
=
=
= 
.
b
9.21,
and
c
12.13.