The formula of the law of cosines looks like the Pythagoras' theorem except for the last part, if C becomes a right angle, the last part will disappear (if the cosine of 90� is 0), so the formula of the law of cosines is simular to Pythagoras' theorem.
The law of cosines relates to the three sides of the triangle to one of the angles.
First, if you know one angle and the other two adjacent sides, then you can determine the opposite angle.
Then, if you know all three sides of a triangle, then you can use it to find any angles.
The law of cosines are:
A2 = B2 + C2 - 2 BC cos a
B2 = A2 + C2 - 2 AC cos b
C2 = A2 + B2 - 2 AB cos c
Back to sine, cosine and tangent or go to the law of sine and the special formulars and angles.
