Why can the Pythagorean theorem be used to compute a vector's magnitude?

The mathematician generalizes the concept to any object that supports sensible addition and scalar multiplication operations.

Conditions: Abstract linear algebra context

Yes, a vector can be translated (moved) to start at the origin without changing its magnitude or direction. In this context, a vector represents a free displacement.

Conditions: The object is a free displacement vector.; Translation must not alter the vector's length.; Translation must not alter the vector's direction.

To find the magnitude of a vector given its components, you substitute the x and y values into the Euclidean magnitude formula $\|\vec{a}\| = \sqrt{x^2 + y^2}$ and simplify. This formula calculates the length of the vector by treating its components as the legs of a right triangle.

Conditions: The vector is defined in a 2D Cartesian coordinate system.; The coordinate axes are orthonormal (perpendicular with the same unit scale).; The magnitude represents the Euclidean length.

When calculating vector magnitude, a negative component is squared, which results in a positive value. This ensures that the direction indicated by the negative sign (e.g., downward or leftward) does not reduce the overall length of the vector.

Conditions: The vector has real components in a Cartesian coordinate system.; The magnitude is computed using the Euclidean formula $\sqrt{x^2 + y^2}$.

The vector magnitude formula uses the square root of the sum of squared components because it is a direct application of the Pythagorean theorem. When a vector is drawn in a Cartesian plane, its horizontal and vertical components form the legs of a right triangle, and the vector itself is the hypotenuse.

Conditions: The vector is represented in an orthonormal Cartesian coordinate system.; The components correspond to perpendicular displacements.; The magnitude is the Euclidean length of the vector.