a - length of side of a square
t - length of side of a triangle
The perimeter of a square: 
The perimeter of a triangle: 
We have the area of a triangle: 
The formula of an area of an equilateral trinagle: 
Substitute:
<em>multiply both sides by 4</em>
<em>divide both sides by
</em>

The perimeter of a triangle: 
Substitute to the formula of a perimeter of a square:
<em>divide both sides by 4</em>

The formula of a diagonal of a square: 
Substitute:

Step-by-step explanation:
Quadrilateral ABCD is inscribed in a circle.
Opposite angles of a Quadrilateral are Supplementary.

Answer:
5/6
Step-by-step explanation:
Its the only fraction that has 0.833333...
.bahajaiakijajwjwjwjwjwjnwjwq
12.7
Using the Pythagorean theorem, you can easily calculate the length of BC.
So:
BC = sqrt(12^2 - 6^2) = sqrt(144 - 36) = sqrt(108) = 10.39230485
Now consider triangle BCD. You know all three angles and one side. Using the law of sines you know that ratio of the sine of each angle over the opposite side is constant. So:
BC/sin(55) = CD/sin(90)
BC/sin(55) = CD/sin(90)
sin(90)BC/sin(55) = CD
1*BC/sin(55) = CD
BC/sin(55) = CD
10.39230485/0.819152044 = CD
12.68666167 = CD
12.7 = CD