Cosine Lawmath trigonometry cosTable of ContentsSourcesFor any triangle:The following is true:$$ c^2 = a^2 + b^2 - 2 \cdot a \cdot b \cdot \cos(\theta) $$Note that the naming of the sides and angle is arbitrary. The formula is true as long as \(\small \theta\) is the angle opposite side c.Sources #WikipediaByju’s