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In this lesson, we will learn how to use trigonometric functions to model various scenarios that demonstrate periodic behavior and apply this in making predictions.

Q1:

The temperature fluctuation on a cold winterβs day (in degrees Celsius) is modeled by π = 3 ο» π 1 2 ( π‘ β 1 4 ) ο + 2 c o s , where π‘ is the time of the day expressed in hours after midnight. At what times of the day was the temperature 0 β C ?

Q2:

Nada is jumping on a trampoline. Her height β above the trampoline , in meters, is given by β = 1 β ο» π 2 π‘ ο c o s , at π‘ seconds after she started jumping.

How many seconds after each rebound does it take her to reach a height of 50 cm during the descent? Round your answer to the nearest tenth of a second.

What fraction of the time is Nada at least 1.2 m above the trampoline? Express your answer as a percentage correct to one decimal place.

Q3:

The outside temperature (in degrees Celsius) on a certain day was modeled with π = 1 2 + 7 ο» π 1 2 ( π‘ β 1 0 ) ο s i n , where π‘ is the time after midnight in hours. At what times of the day was the temperature 1 0 β C ? Give your answer to the nearest minute using a 24-hour format.

Q4:

The daily solar irradiation π οΉ / ο W m 2 on a point just above Earthβs atmosphere π days after the summer solstice is given by π ( π ) = 1 3 6 0 + 4 6 οΌ 2 π 3 6 5 π ο c o s . How many times per year is the daily solar irradiation 1 3 5 0 W/m^{2}? How many days after the solstice does this occur?

Q5:

The number of hours of daylight in Paris depends on the season, and it is modeled by π = 1 2 β 4 οΌ 2 π 3 6 5 ( π‘ + 1 0 ) ο c o s , where π‘ is the number of the day in a year (January 1 is day 1). According to this model, when is the length of the day in Paris 10 hours?

Q6:

Farida and her friends got on a Ferris wheel. When they entered the cabin at 3:15 pm, they were 5 m above the ground. The height of the cabin minutes after they got into it is given by . When were they 40 m above the ground? Give your answer to the nearest minute.

Q7:

A Ferris wheel is 45 m in diameter. A ride takes 10 minutes and consists of one complete revolution, starting and finishing at the lowest point. When riders board the Ferris wheel, their seats are 4 m above the ground. How much of a ride is spent more than 17 m above ground? Give your answer to the nearest second.

Q8:

A spring is fixed at one end and hangs vertically. Its lower end is pulled 10 cm down from its equilibrium position and released. It performs 18 oscillations every second, and the amplitude of the oscillations decreases by 1 5 % each second. Find a function that models π· , the displacement of the end of the spring from its equilibrium position, in terms of π‘ , the time in seconds, after it was released.

Q9:

The height of a piston, β , in inches can be modeled by the equation π¦ = 2 π₯ + 5 c o s , where π₯ represents the crank angle. Find the height of the piston when the crank angle is 5 5 β .

Q10:

Outside temperatures over 24 hours can be modeled as a sinusoidal function. On a day with an average temperature of 7 0 β F , the maximum temperature of 8 4 β F is recorded at 6 pm. Find, to the nearest degree, the temperature at 7 am.

Q11:

In a certain location, the temperature over the course of a day varies between a minimum of 6 4 β F at 6 am and a maximum of 8 6 β F . If the temperature is modeled by a sinusoidal function, what is the first time in the day when the temperature is 7 0 β F ?

Q12:

The percentage grade of a road is defined as the change in height of the road over a 100-foot horizontal distance. For example, if the road rises 5 feet over a horizontal distance of 100 feet, it will have a 5 % grade.

What is the percentage grade of a road that makes an angle of 4 β with the horizontal?

Q13:

A spring is fixed at one end and hangs vertically. Its lower end is pulled 10 cm down from its equilibrium position and released. It performs 22 oscillations every second, and, after 3 seconds, the amplitude of the oscillations is 2 cm. How long does it take for the amplitude of its oscillations to decrease to 0.1 cm? Give your answer to three decimal places.

Q14:

Fady and Rania went swimming in the sea at 2 pm, when it was high tide. The change in the height of water with respect to the annual average is given by , where is the time, in hours, after any high tide.

At what time was the next high tide?

When will it be high tide in the afternoon three days later?

They want to go back to the same beach three days later, in the afternoon, and would like the height of the water to be at least 4 metres above the annual height average. Between what times should they go?

Q15:

Outside temperatures over 24 hours can be modeled as a sinusoidal function. On a day with an average temperature of 8 5 β F , the maximum temperature of 1 0 5 β F is recorded at 5 pm. Find, to the nearest degree, the temperature at 9 am.

Q16:

A particle moves along the π₯ -axis so that its displacement from the origin π after π‘ seconds is 7 ( 1 2 π‘ ) s i n metres. Find the times at which the particleβs displacement is 7 2 metres. Use π to denote an arbitrary non-negative integer.

Q17:

Outside temperatures over 24 hours can be modeled as a sinusoidal function with the daily maximum occurring after midday. On a day when the average temperature is first recorded at 10 am, the temperature varies between 4 7 β F and 6 3 β F . After midnight, when is the first time the temperature reaches 5 1 β F ?

Q18:

The sea ice area around the South Pole fluctuates between about 18 million square kilometers in September to 3 million square kilometers in March. Assuming a sinusoidal fluctuation, when are there more than 15 million square kilometers of sea ice? Give your answer as a range of dates to the nearest day.

Q19:

The slope for a wheelchair ramp for a house has to be 1 1 2 . If the vertical distance from the ground to the door bottom is 2.5 ft, find the distance the ramp has to extend from the house in order to comply with the needed slope.

Q20:

Maged sits on a pier, his feet dangling 60 cm below the pier. The pier is usually 80 cm above the lake. But this is a windy day, and waves make the depth of the lake oscillate. The depth of the lake under the pier is given, in meters, by , where is the depth of the lake on a quiet day, and is the time in seconds. What fraction of the time does Maged have his feet under water? Express your answer as a percentage correct to one decimal place.

Q21:

The sea ice area around the North Pole fluctuates between about 6 million square kilometres on September 1 to 14 million square kilometres on March 1. Assuming a sinusoidal fluctuation, when are there less than 9 million square kilometres of sea ice? Give your answer as a range of dates to the nearest day.

Q22:

A spring is fixed at one end and hangs vertically. Its lower end is pulled 21 cm down from its equilibrium position and released. It performs 20 oscillations every second, and, after 6 seconds, the amplitude of the oscillations is 4 cm. How long does it take for the amplitude of its oscillations to decrease to 0.1 cm? Give your answer to three decimal places.

Q23:

Dalia and Maged are at home. They see a bucket suspended on an elastic string going up and down in front of their window. They record the times at which they saw the bucket appear, disappear, appear again, and so on, as shown in the table.

What is the period of the bucketβs movement?

The vertical displacement of the bucket with respect to the centre of its movement can be modeled with the function , where is the period above and , in seconds, is sized as in the table. Given that the height of Dalia and Magedβs window is 1.2 m, what is the amplitude of the function? Give your answer to one decimal place.

At what value of is the bucket at its highest point?

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