STEP 1: find side $ a $
To find side $ a $ use formula:
$$ B = \dfrac{ \sqrt{ 3 } \cdot a^2 }{ 4 }$$After substituting $B = 7.2\, \text{cm}$ we have:
$$ 7.2\, \text{cm} = \dfrac{ \sqrt{ 3 } \cdot a^2 }{ 4 }$$ $$ 7.2\, \text{cm} \cdot 4 = \sqrt{ 3 } \cdot a^2 $$ $$ 28.8\, \text{cm} = \sqrt{ 3 } \cdot a^2 $$ $$ a^2 = \dfrac{ 28.8\, \text{cm} }{ \sqrt{ 3 } } $$ $$ a^2 = 16.6277\, \text{cm} $$ $$ a = \sqrt{ 16.6277\, \text{cm} } $$$$ a \approx 4.0777 $$STEP 2: find height $ h $
To find height $ h $ use formula:
$$ h = \dfrac{ \sqrt{ 3 } \cdot a }{ 2 } $$After substituting $a = 4.0777\, \text{cm}^0$ we have:
$$ h = \dfrac{ \sqrt{ 3 } \cdot 4.0777 }{ 2 } $$$$ h = \dfrac{ 7.0628 }{ 2 } $$ $$ h \approx 3.5314 $$