Your two cards could be a negative six and a positive two.
Answer: 
-3 times the square root of 5
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Explanation:
Let 
Replace all the root 5 terms with x and we go from

to

From here, combine like terms to get

and the last thing to do is replace the x with sqrt(5)

Meaning that,


Answer:

Step-by-step explanation:
The given trigonometric equation is

We take the inverse cosine of both sides to obtain;


Group similar terms t obtain;


D, 8.5
a squared + b squared = c squared for the sides and hypotenuse of the triangle.
6^2 + 6^2 = c^2
36 + 36 = c^2
72 = c^2
c = square root of 72, 8.49