Question

4. A poster of height 36 in. is mounted on a wall so that its lower edge is 12 in. above the eye level
of an observer. How far from the wall should the observer stand so that the viewing angle 
subtended at his eye by the poster is as large as possible?

Answer 1

answer is 24. let two angles k1 and k2 such that tan(k1) is 12 divided by x where x is the distance to be found. and tan( k1 + K2) is 48 divided by x. make quadratic in x where u will get 1296- 2304tank2 in underroot. now tan k2 comes to be 0.75 . soving further x is 24.