How did you get that number?
What are you confused on?
A _____________________B
D _________________C
By alternate interior angles, DCA = CAB. All angles in a triangle add up to 180. Can you solve it?
How? Must be dark magic, or maybe a typo.
Hint:
Shaded = Square - 4 quarter circle
4 quarter circles = full circle
Full circle area = \({\pi}r^2\)
Square area = \(s^2\)
In this case, the side of the square is twice the radius of the circle.
Here: https://www.wikihow.com/Find-the-Area-of-a-Regular-Pentagon
Hint: It is a 45 - 45 - 90 triangle.
That means the area is (leg times leg) divided by two. The leg is \(\frac{6\sqrt{2}}{\sqrt{2}}\).
See this: https://www.wikihow.com/Calculate-Maximum-Revenue
This was posted by me. It is in algebraic proof.
