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Use a calculator and reciprocal relationships to find the ratio correct to four decimal places. sec(559) Need Help? Read It 16. [-/1 Points] DETAILS ALEXGEOM7 11.3.036. In the following exercise, we expand the list of trigonometric identities. As you may recall, an identity is a statement that is true for all permissible choices of the variable. Consider the following figure. B B a b (a) For a = 0º, prove the identity csc(a) = 1 sin(a) (Hint: sin(a) = :0) = Substituting the given value of sin(a) and then simplifying, we have the following. 1 1 sin(a) = 1 But simplified and in terms of side lengths, csc(a) = as well, so csc(a) = sin(a) (b) Use your calculator to determine csc(18.7°). (Round your answer to four decimal places.) Need Help? Read It

17. [-/1 Points] DETAILS ALEXGEOM7 11.3.039. When her airplane is descending to land, the pilot notes an angle of depression of 50 110 ft If the altimeter shows an altitude reading of 110 ft, what is the distance x from the plane to touchdown? Give your answer to the nearest tenth of a foot. x = ft Need Help? Read It 18. [-/1 Points] DETAILS ALEXGEOM7 11.3.040. Kristine observes the top of a lookout tower from a point 280 ft from its base. 400 280 ft If the indicated angle of elevation measures 40º, how tall is the tower? Give your answer to the nearest tenth of a foot. Need Help? Read It