Final answer:
The purpose of using the Pythagorean theorem in physics is to find the magnitude of a vector (Option C), especially when adding or subtracting vectors that are perpendicular to each other.
Step-by-step explanation:
The Pythagorean theorem is used in physics to determine the magnitude of a vector.
When adding or subtracting vectors, the Pythagorean theorem can be used to find the length or magnitude of the resultant vector. This theorem is applicable when the vectors are perpendicular to each other.
For example, if we have two vectors, A and B, that are at right angles to each other, we can use the Pythagorean theorem to calculate the magnitude of the resultant vector obtained from their addition.
The Pythagorean theorem states that the square of the hypotenuse (C) is equal to the sum of the squares of the other two sides (a and b): C² = a² + b².
Thus, the correct answer to the question is: (Option C) To find the magnitude of a vector.