Dave is going to leave academia and go into business building grain silos. a grain silo is a cylinder with a hemispherical top, used to store grain for farm animals. here is a 3d view, a cross-section, and the top view. if dave is standing next to a silo of cross-sectional radiusr = 7feet at the indicated position, his vision will be partially obstructed. find the portion of the y-axis that dave cannot see. (hint: let a be the x-coordinate of the point where line of sight #1 is tangent to the silo; compute the slope of the line using two points (the tangent point and (12, on the other hand, compute the slope of line of sight #1 by noting it is perpendicular to a radial line through the tangency point. set these two calculations of the slope equal and solve for a. enter your answer using interval notation. round your answer to three decimal places.)