Answer:
DB = 6
Step-by-step explanation:
See the attached figure to the question.
Since O is the center of the given circle, so AB and CD are diameters of the circle.
Hence, AO = CO = OD = OB = radius of the circle = 6
In Δ OAC, we have AO = OC. Hence, ∠ A = ∠C = 60° {Given that ∠OAC = 60°}
So, ∠ AOC will automatically become 60°. {As the sum of all the angles of a triangle is 180°}
So, Δ AOC is equilateral triangle.
Now, ∠ AOC = ∠ BOD = 60° {Since, they are vertically opposite angles}
Now, in Δ BOD, we have DO = OB. Hence, ∠ D = ∠ B = 60° {As the sum of all the angles of a triangle is 180°}
So, Δ BOD is also an equilateral triangle.
So, DB = BO = DO = 6. (Answer)
Answer:
There is a 99.99998% probability that at least one valve opens.
Step-by-step explanation:
For each valve there are only two possible outcomes. Either it opens on demand, or it does not. This means that we use the binomial probability distribution to solve this problem.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinatios of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
In this problem we have that:

Calculate P(at least one valve opens).
This is 
Either no valves open, or at least one does. The sum of the probabilities of these events is decimal 1. So:


So


Finally

There is a 99.99998% probability that at least one valve opens.
Answer:
2 to the power of one sixth
Step-by-step explanation:
Assuming you don't already know this, any type of root can be expressed as an exponent. Generally speaking:
![\sqrt[n]{x} = {x}^{ \frac{1}{n} }](https://tex.z-dn.net/?f=%20%5Csqrt%5Bn%5D%7Bx%7D%20%20%3D%20%20%7Bx%7D%5E%7B%20%5Cfrac%7B1%7D%7Bn%7D%20%7D%20)
So you can rewrite the given fraction as

and then reduce as you normally would. That is, if the bases of the numerator and denominator are the same, then you can subtract the denominator's exponent from the numerator's exponent like so:

Since

the answer is
![{2}^{ \frac{1}{6} } \: or \: \sqrt[6]{2}](https://tex.z-dn.net/?f=%20%7B2%7D%5E%7B%20%5Cfrac%7B1%7D%7B6%7D%20%7D%20%20%5C%3A%20or%20%5C%3A%20%20%5Csqrt%5B6%5D%7B2%7D%20)
The answer is A hun! :)
explanation: just trust me haha