The standard deviation assumes a negative value when

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.

What is the answer to question 11? will give extra points! include a explanation (reasonable) for you : )

Suppose that a disk drive has 5,000 cylinders, numbered 0 to 4,999. the drive is currently serving a request at cylinder 2,150, and the previous request was at cylinder 1,805. the queue of pending requests, in fifo order, is: 2069, 1212, 2296, 2800, 544, 1618, 356, 1523, 4965, 3681