How many seven digit phone numbers can be formed if repetition is allowed

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

5/6+7/8what is the answer sealsdbdbshd

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).