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How do you find the magnitude of a vector given its x and y components?

To find the magnitude of a vector given its components, you substitute the x and y values into the Euclidean magnitude formula ∥a⃗∥=x2+y2\|\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.

Reasoning, step by step

  1. Identify the x-component and y-component of the vector.
  2. Substitute these values into the formula ∥a⃗∥=x2+y2\|\vec{a}\| = \sqrt{x^2 + y^2}.
  3. Square each component individually.
  4. Add the squared values together.
  5. Take the positive square root of the sum.

Example

For the vector a⃗=(5,−3)\vec{a} = (5, -3), the magnitude is calculated as ∥a⃗∥=52+(−3)2=25+9=34\|\vec{a}\| = \sqrt{5^2 + (-3)^2} = \sqrt{25 + 9} = \sqrt{34}.

Common misconceptions

  • Thinking that a negative component reduces the magnitude; squaring a negative number yields a positive result, so (−3)2=9(-3)^2 = 9.
  • Applying the formula unchanged to nonorthogonal coordinate systems.

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