When x≤a,
At △OEG and △OFC,
∠GOE=∠COF (male * * * angle), ∠ AEG =∠ AFC = 90,
∴△OEG∽△OFC,OEOF=GECF,
∴ya? (x? y)=hl,
∴y=-hl? hx+ahl? h,
∫a, H and L are all fixed constants,
The coefficient of the independent variable x is a fixed value,
∴ This function image must be a linear function image, that is, a straight line;
The length of the shadow becomes shorter and shorter as it gets closer to the light, becomes a point below the light, and then becomes larger as it gets farther and farther away from the light.
So choose a.