Step-by-step explanation:
The diagonal separates the rectangle into 2 triangles. Therefore to calculate the length of the diagonal we can use the Pythagorean theorem.
Let the diagonal equal x
Therefore:
[tex] {x}^{2} = {l}^{2} + {b}^{2} [/tex]
[tex] {x}^{2} = {20}^{2} + {42}^{2} [/tex]
[tex] {x}^{2} = 400 + 1764[/tex]
[tex] {x}^{2} = 2164[/tex]
[tex]x = \sqrt{2164} [/tex]
[tex]x = 2 \sqrt{541} \: or \: 46.52[/tex]
