So you question is most likely about a triangle DEF with the 3 angles being named D, E, F. The triangle would look something like the image attached below.
If that is what is being asked then i need more info to answer but
By Definition it would be 180 degrees.
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A ≈ 78.46 ft
To find the answer just look up the formula for finding area with circumference and plug in the circumference
Solution:
Let x = the number of $70 seats sold
Let y = the number of $20 seats sold
x+y ≤ 20,000
70x+20y > 500,000
Answer:

Step-by-step explanation:
Given
See attachment
Required
The area of the semicircle
First, we calculate the hypotenuse (h) of the triangle
Considering only the triangle, we have:
--- cosine formula
Make h the subject



The area of the semicircle is then calculated as:

This gives:


