STEP 1: find side $ a $
To find side $ a $ use formula:
$$ R = \dfrac{ \sqrt{ 3 } \cdot a }{ 3 } $$After substituting $R = 14\, \text{cm}$ we have:
$$ 14\, \text{cm} = \dfrac{ \sqrt{ 3 } \cdot a }{ 3 } $$ $$ \sqrt{ 3 } \cdot a = 14\, \text{cm} \cdot 3 $$ $$ \sqrt{ 3 } \cdot a = 42\, \text{cm} $$ $$ a = \dfrac{ 42\, \text{cm} }{ \sqrt{ 3 } } $$ $$ a = 14 \sqrt{ 3 }\, \text{cm} $$STEP 2: find area $ A $
To find area $ A $ use formula:
$$ A = \dfrac{ \sqrt{ 3 } \cdot a^2 }{ 4 } $$After substituting $a = 14 \sqrt{ 3 }\, \text{cm}$ we have:
$$ A = \dfrac{ \sqrt{ 3 } \cdot \left( 14 \sqrt{ 3 }\, \text{cm} \right)^{2} }{ 4 } $$ $$ A = \dfrac{ \sqrt{ 3 } \cdot 588\, \text{cm}^2 }{ 4 }$$ $$ A = \dfrac{ 588 \sqrt{ 3 }\, \text{cm}^2 }{ 4 }$$ $$ A = 147 \sqrt{ 3 }\, \text{cm}^2 $$