27.5 Putting Vectors to Work: Geometry and Physics
Point 3 of 7
27.5.3 Proving the Law of Cosines with Vectors
Core idea
Write the third side as the difference of the other two, square it by dotting it with itself, and c²=a²+b²−2ab cosC falls right out.
Module goal. Use vectors as a toolkit to prove geometric theorems, compute lengths and angles, handle forces and velocities, and lay the groundwork for vectors in space.
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