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12) [1] (/5) Prove the following trigonometric identity. 1- sin x 1+ sin x = 2 tan x sec x 13) [A] (/2) A city planning committee estimates that the population of the city will chan with respect to the time, t in years, it takes to build new homes. The population, P in thousands, is according to the equation P(t) =10v1+t . Determine the average rate o change in population, to two decimal places, between years 3 and 15