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Use the fact that sin(angle) = opposite/hypotenuse

or angle = sin^-1(opposite/hypotenuse)

$sin \vartheta = \frac{5}{12}$

$\vartheta = sin^{-1}(\frac{5}{12})$

which is approximately 24.6243°

Therefore, the missing angle is 24.6243° which is about 0.429775 radians (all corr. to 6 sig. fig.)