Dave is going to leave academia and go into business buildinggrain 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= 8

feet at the indicated position, his vision will be partially obstructed. Find the portion of they-axis that Dave cannot see. (Hint: Leta be thex-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, 0)). 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 fora. Enter your answer using interval notation. Round your answer to three decimal places.)

I have been stuck on this problem, any help on how to approach it? Thank you!