STEP 1: find side $ a $
To find side $ a $ use formula:
$$ d = \sqrt{ 2 } \cdot a $$After substituting $ d = 6.7 $ we have:
$$ 6.7 = \sqrt{ 2 } \cdot a $$ $$ a = \dfrac{ 6.7 }{ \sqrt{ 2 } } $$ $$ a \approx 4.7376 $$STEP 2: find base area $ B $
To find base area $ B $ use formula:
$$ B = a^2 $$After substituting $ a = 4.7376 $ we have:
$$ B = 4.7376^2 $$ $$ B = 22.445 $$