If you draw a sketch, look at some ratios, you will find a nice relationship between the two angles of depression.
give me the solution from the top of a building the angle of depression of a point on the same horizontal plane with the base of the building is observed to be 60 degree what will be the angle of depression of the same point when viewed from a position one third of the way up the building
No, I'm not going to simply give you the answer. I will help you figure out how to do the problem...if you are willing to show some effort.
Put pen/pencil to paper, and draw a sketch. Tell us what you find, and we will be glad to help.
Okay, I assume you have labeled the distances and angles...
Using trigonometry, what is the ratio of the horizontal distance to the point to the height of the building?
Hint: use the tangent function. Do you see why?
edit: Or use the special angles within the larger triangle.
The reason the tangent function is useful here, is that it relates an angle in a right triangle to the ratio of the opposite to the adjacent side.
If , what do the opposite and adjacent sides of the larger triangle represent?