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\frac{\mathrm{d} \theta}{\mathrm{dt}}=\frac{\sin ^{2}(\theta) \frac{\mathrm{d} \mathrm{x}}{\mathrm{dt}}}{-40}=\frac{\sin ^{2}(0.1745)(-25)}{-40} \approx \frac{(0.1736)^{2}(-25)}{-40} \approx 0.0188