What does rectangular notation express a vector as?

Rectangular notation expresses a vector as a complex number by specifying its components along the axes in a coordinate system. In this way, a vector in two-dimensional space, for example, can be represented as an ordered pair of values (x, y), which can also be interpreted as a complex number x + yi, where x is the horizontal component and y is the vertical component. This representation allows for easy manipulation of vectors using arithmetic operations similar to those used with complex numbers, making it a powerful tool in various fields such as physics and engineering.

Other options do not capture the essence of what rectangular notation does. A line segment could represent the magnitude and direction of a vector, but it does not give precise coordinates. A scalar represents only magnitude without direction, which is insufficient for a vector description. A graph can visually depict a vector but does not express it in the mathematical form that rectangular notation provides.