2.16 : Dot Product: Problem Solving

The dot product is a powerful tool in problem-solving involving vectors, given that the dot product of two vectors is the product of their magnitudes and the cosine of the angle between them measured anti-clockwise. Solving problems involving the dot product requires understanding its properties and developing a step-by-step process to solve them. Here are the main steps to follow when solving any general problem involving the dot product:

Identify the problem: Start by reading the problem and identifying the question that needs to be answered. This will enable you to determine the purpose and direction for solving the problem.

Define the vectors: List the given vectors and represent them in the Cartesian or component form.

Decide which operation to use: The dot product is appropriate when the problem involves finding the angle between two vectors, calculating the component of a vector along a given direction, testing orthogonality, or finding the projection of one vector onto another vector. Ensure that the problem requires the use of the dot product before proceeding.

Calculate the dot product: Multiply the corresponding components of the two vectors and sum their products. This gives the value of their dot product.

Verify the solution: Check your solution to ensure that it satisfies the given conditions in the problem. Be sure to round off the answer appropriately and include the correct units where necessary.

The angle between two vectors can be obtained from the inverse cosine of the dot product of the two vectors divided by the product of the magnitudes of the two vectors. The dot product can also be employed to find the component of a vector along a given direction by projecting it onto a unit vector in the desired direction. This technique is particularly useful for decomposing complex vector problems into simpler components. Additionally, the dot product can be used to test orthogonality between two vectors. If their dot product is zero, the vectors are orthogonal, meaning they are perpendicular to each other. Lastly, the projection of one vector onto another can be found using the dot product by multiplying the magnitude of the first vector by the cosine of the angle between the two vectors.