68. Relative Aperture. The relative aperture, or f-stop, of a 23.5-mm lens is directly proportional
to the focal length F of the lens. If a lens with a
150-mm focal length has an f-stop of 6.3, find the
f-stop of a 23.5-mm lens with a focal length of
80 mm.

In one day there are too high tides into low tides and equally spaced intervals the high tide is observed to be 6 feet above the average sea level after six hours passed a low tide occurs at 6 feet below the average sea level in this task you will model this occurrence using a trigonometric function by using x as a measurement of time assume the first high tide occurs at x=0. a. what are the independent and dependent variables? b. determine these key features of the function that models the tide: 1.amplitude 2.period 3.frequency 4.midline 5.vertical shift 6.phase shift c. create a trigonometric function that models the ocean tide for a period of 12 hours. d.what is the height of the tide after 93 hours?