Law of cosines
Law Of Cosines
The law of cosnies extends the use of the Pythagorean theorem. It enables us to find the length of the opposite side of a known angle when any enclosed angle is known. It also enables us to find unknown angles when three sides are known.It reads as follows:
a2 = b2 + c2 - 2bc cos a
Similiarly, we may substitute sides and angles to complete the law to read:
b2 = a2 + c2 - 2ac cos b
and
c2 = a2 + b
· Pythagorean theorem