1. AB is a tangent line to the circle C at point B ∴ AB⊥BC ∴ Δ ABC is a right triangle , ∠B = 90° ∴ AC² = AB² + BC² BC = radius = 4,000 AC = 4,000 + 22,000 = 26,000 ∴ AC² = AB² + BC² = 4,000² + 26,000² = 692 * 10^6 ∴ AC = √( 692 * 10^6 ) ≈ 26,306 mi
2. <span>∠BAC = 9° </span> <span> Δ ABC is a right triangle , ∠B = 90°</span> <span> ∠CBA = 90° </span> ∴ ∠BCA = 180° - (90° + 9°) = 81° ∴ the measure of arc BD which facing the <span>satellite = 2 * 81° = 162° </span> while the total angel of the circle = 360° ∴ <span>The percent of the Earth’s equator which is within range of the satellite’s signal = 162/360 = 0.45 = 45% </span>
