Question:
ABCD is a rectangle whose three vertices are B(4, 0), C(4, 3) and D(0, 3). Find the length of one of its diagonal.
Solution:
The given vertices are B(4, 0), C(4, 3) and D(0, 3). Here, BD is one of the diagonals. So
$B D=\sqrt{(4-0)^{2}+(0-3)^{2}}$
$=\sqrt{(4)^{2}+(-3)^{2}}$
$=\sqrt{16+9}$
$=\sqrt{25}$
$=5$
Hence, the length of the diagonal is 5 units..