Answer:
Step-by-step explanation:
Observe in the figure given in the exercise that four right triangles are formed.
In this case you can use the following Trigonometric Identity to solve this exercise:
From the figure you can identify that:
Then, you can substitute values:
The next step is to solve for DE in order to find its value. This is:
Finally, rounding the result to the nearest tenth, you get that this is: