\[ \therefore \mathrm{m}(\angle \mathrm{DME})=360^{\circ}-\left(90^{\circ}+90\right. \] TRY 5 by Yourself In the opposite figure : \( \overline{\mathrm{BC}} \) is a diameter of the circle M , \( \overline{\mathrm{MD}} \perp \overline{\mathrm{AB}} \) where \( \overline{\mathrm{MD}} \cap \overline{\mathrm{AB}}=\{\mathrm{D}\} \) , \( \mathrm{m}(\angle \mathrm{C})=40^{\circ} \) and \( \mathrm{AC}=8 \mathrm{~cm} \). Find: (2) The length of \( \overline{\mathrm{MD}} \) \( 1 \mathrm{~m}(\angle \mathrm{DMB}) \)
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To find the length of \( \overline{\mathrm{MD}} \) and \( \mathrm{m}(\angle \mathrm{DMB}) \), we can apply some properties of circles and triangles. Since \( \overline{\mathrm{BC}} \) is a diameter, angle \( \mathrm{C} \) creates a right triangle with points \( \mathrm{D}, \mathrm{M}, \) and \( \mathrm{B} \). By using the sine function in triangle \( \mathrm{ACD} \), we have: \[ \sin(\mathrm{m}(\angle C)) = \frac{\mathrm{MD}}{\mathrm{AC}} \implies \mathrm{MD} = \mathrm{AC} \cdot \sin(40^{\circ}) \approx 8 \cdot 0.6428 \approx 5.14 \text{ cm} \] For \( \mathrm{m}(\angle DMB) \), recognize that \( \mathrm{m}(\angle DMB) \) is supplementary to \( \mathrm{m}(\angle C) \) as they span through the point \( \mathrm{M} \) on the circle. Thus: \[ \mathrm{m}(\angle DMB) = 180^{\circ} - 40^{\circ} = 140^{\circ} \] Now you have both the length and the angle calculated, ready to impress your classmates! Understanding how angles and circles interact can feel like a magical dance! Consider how ancient Greek mathematicians, including Archimedes, made discoveries about circles and angles that are widely used even today. Their methodologies laid the foundation for modern trigonometry and geometry, allowing us to quantify and understand spatial relationships in our universe! When working with circle geometry, a common mistake is misapplying the inscribed angle theorem, which states that an inscribed angle is half of the measure of the arc it subtends. Always ensure to keep a check on which angles are subtended and whether they are central or inscribed; this often leads to misunderstanding the relationships between the angles and arcs in circle problems!