STEP 1: find side $ a $
To find side $ a $ use formula:
$$ r = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $ r = \frac{ 39 }{ 2 } $ we have:
$$ \frac{ 39 }{ 2 } = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$ $$ \sqrt{ 3 } \cdot a = \frac{ 39 }{ 2 } \cdot 2 $$ $$ \sqrt{ 3 } \cdot a = 39 $$ $$ a = \dfrac{ 39 }{ \sqrt{ 3 } } $$ $$ a = 13 \sqrt{ 3 } $$STEP 2: find area $ A $
To find area $ A $ use formula:
$$ A = \dfrac{ 3 \sqrt{ 3 } \cdot a^2 }{ 2 } $$After substituting $ a = 13 \sqrt{ 3 } $ we have:
$$ A = \dfrac{ 3 \sqrt{ 3 } \cdot \left(13 \sqrt{ 3 }\right)^2 }{ 2 } $$ $$ A = \dfrac{ 3 \sqrt{ 3 } \cdot 507 }{ 2 }$$ $$ A = \dfrac{ 1521 \sqrt{ 3 } }{ 2 }$$ $$ A = \frac{ 1521 \sqrt{ 3}}{ 2 } $$