Find the square of the X-component of the vector. For example, if the given X-component is 3 N, then the square of the X-component is 9 N^2 = (3 N)^2 = (X-component)^2.
Find the square of the Y-component of the vector. For example, if the given Y-component is 4 N, then the square of the Y-component is 16 N^2 = (4 N)^2 = (Y-component)^2.
Add the square of the X-component to the square of the Y-component. For example, if the given X-component is 3 N and the Y-component is 4 N, then the sum of the component squares is 25 N^2 = 9 N^2 + 16 N^2 = (3 N)^2 + (4 N)^2 = (X-component)^ 2 + (Y-component)^2.
Find the magnitude of the vector by determining the square root of the sum of the squares of the components. For example, if the given X-component is 3 N and the Y-component is 4 N, then the square root of the sum of the component squares is 5 N = (25 N^2)^0.5 = (9 N^2 + 16 N^2)^0.5 = ((3 N)^2 + (4 N)^2)^0.5 = ((X-component)^ 2 + (Y-component)^2)^0.5.