Let's try to draw a rough diagram of the problem:
From here, we can dissect a triangle as shown below:
From this diagram, we are going to find H, the height of the skyscraper.
We already know that part of the side length "H" is 1200 feet. We need to find the other part of "H". Let's label it h1.
Finding h1:
Thus,
The height of the skyscraper is 1620.12 feet