∴: The coordinate of point C is (200,0).

∫tanα= 12

∴ The slope of the straight line CD is 12.

The linear CD equation is: y = 12 (x? 200)

(2) remember P(x, y),

∫PA≥OC = 200 > AB，

∴∠APB is an acute angle

tan∠APB=|kPA？ kPB 1+kPA？ kPB|=|y？ 220x？ y？ 300x 1+y？ 220x？ y？ 300x |

=805x4+ 128000x？ 360≤2 1 1

When 5x4 = 128000x, take the equal sign, that is, x=320 and y=60.

∴ When the observer is located at P (320 320,60), the maximum viewing angle is arctan2 1 1.