STEP 1: find height $ h $

To find height $ h $ use formula:

$$ h = 2 \cdot r $$

After substituting $r = 18\, \text{cm}$ we have:

$$ h = 2 \cdot 18\, \text{cm} $$ $$ h = 36\, \text{cm} $$

STEP 2: find angle $ \alpha $

To find angle $ \alpha $ use formula:

$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ h }{ d_1 } $$

After substituting $h = 36\, \text{cm}$ and $d_1 = 36\, \text{cm}$ we have:

$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ 36\, \text{cm} }{ 36\, \text{cm} } $$ $$ \sin \left( \frac{ \alpha }{ 2 } \right) = 1 $$ $$ \frac{ \alpha }{ 2 } = \arcsin\left( 1 \right) $$ $$ \frac{ \alpha }{ 2 } = 90^o $$

Angle $ $ \alpha $ $ has to be lesser than 90 degrees $ \Longrightarrow $ The problem has no solution.

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