19. When the Sun first disappears while lying down, your line of sight to the top of the Sun is tangent to the Earth’s surface at point A shown in the figure. As you stand, elevating your eyes by a height h, the line of sight to the Sun is tangent to the Earth’s surface at point B. Letdbe the distance from point B to your eyes. From Pythagorean theorem, we have 222 22()2drrhrrhh+=+=++or2,hhwhereris the radius of the Earth. Since rh5, the second term can be dropped, leading to 22h≈. Now the angle between the two radii to the two tangent
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