Question

ABCD has vertices A(4, 0), B(0, 4), C(–4, 0), and D(0, –4). Determine whether ABCD is a rectangle, rhombus, or square. List all that apply.

Answer 1

Explanation:

let's consider BA and CD as one pair of sides, and CB and DA as the second pair of sides.

the slope BA = -1

as x changes +4 (from 0 to 4), and y changes -4 (from 4 to 0).

the slope of CD = -1

as x changes +4 (from -4 to 0) and y changes -4 (from 0 to -4).

so, both lines are indeed parallel.

the slope CB = +1

as x changes +4 (from -4 to 0) and y changes +4 (from 0 to 4)

the slope of DA = +1

as x changes +4 (from 0 to 4) and y changes +4 (from -4 to 0)

so, these 2 lines are also parallel to each other and perpendicular to the first 2 lines (x and y in the slope ratio upside-down, and the sign is flipped).

therefore, we have only 90° angles here.

and the sums of the x and y coordinate differences are the same for every side, so all sides are equally long.

therefore, this is a square.

and with that it is automatically also a rectangle and a rhombus.