law of cosines
posted by Anonymous .
law of cosines
m<c=60, a=12,b=15 triangle

The law of cosines is:
a^2 = b^2 + c^2  2cosA
or
b^2 = a^2 + c^2  2cosB
or
c^2 = a^2 + b^2  2cosC
the lower case letters are sides, the capital letters are for angles. For this problem, you would do
c^2 = 12^2 + 15^2  2cos60
That gives you side c. After that, you should be able to use the law of sines to find the other two angles of the triangle.