Three vertices of △ABC have coordinates: A(1, 1), B(4, 1), and C(4, 5). What are the cosines of the angles of the triangle? cos ∠ABC =?

cos ∠BAC = ?

cos ∠ACB =?

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.