To find side $ a $ use Pythagorean Theorem:

$$ h^2 + \frac{ a^2 }{ 4 } = s^2 $$

After substituting $h = 72\, \text{cm}$ and $s = 97\, \text{cm}$ we have:

$$ \left( 72\, \text{cm} \right)^{2} + \frac{ a^2 }{ 4 } = \left( 97\, \text{cm} \right)^{2} $$ $$ \frac{ a^2 }{ 4 } = \left( 97\, \text{cm} \right)^{2} - \left( 72\, \text{cm} \right)^{2} $$ $$ \frac{ a^2 }{ 4 } = 9409\, \text{cm}^2 - 5184\, \text{cm}^2 $$ $$ a^2 = 4225\, \text{cm}^2 \cdot 4 $$ $$ a^2 = 16900\, \text{cm}^2 $$ $$ a = \sqrt{ 16900\, \text{cm}^2 } $$$$ a = 130\, \text{cm} $$

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