STEP 1: find side $ a $
To find side $ a $ use formula:
After substituting $A = 36\, \text{cm}$ we have:
$$ A = a^2 $$ $$ a^2 = 36\, \text{cm} $$ $$ a = \sqrt{ 36\, \text{cm} } $$ $$ a = 6 $$STEP 2: find diagonal $ d $
To find diagonal $ d $ use formula:
$$ d = \sqrt{ 2 } \cdot a $$After substituting $a = 6\, \text{cm}^0$ we have:
$$ d = \sqrt{ 2 } \cdot 6 $$ $$ d = 6 \sqrt{ 2 } $$