Exercise 15 Page 558

Practice makes perfect

a We have been given a function that shows time t it takes a dropped object to fall h feet.

t=1/4sqrt(h) We will graph this function using a graphing calculator. To do so, we will first slightly modify our function by replacing t with y and h with x. Let's do it!

t=1/4sqrt(h) ⇔ y=1/4sqrt(x) To draw a graph on a calculator, we press the Y= button and type the function in one of the rows. Having written the function, we can push GRAPH to draw it.

Now, we will describe the domain and range of the given function. The domain is the set of non-negative real numbers because the height cannot be negative. By the same reasoning, the range is also the set of non-negative real numbers. Domain:& h ≥ 0 Range:& t ≥ 0

b We have been told that a stone was dropped from the New River Gorge Bridge and it took 7.4 seconds to reach the water. To find the height of the bridge, we will use the TRACE button of the graphing calculator. We will first change the viewing window settings so that we can see y=7.4.

Next, we will push the TRACE button. Then, we will try to get y=7.4 using arrow keys on the graphing calculator.

The height of the bridge is about 876 feet.

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Exercise 15 Page 558

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