Core Connections Integrated III, 2015
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Core Connections Integrated III, 2015 View details
1. Section 9.1
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Exercise 7 Page 433

Draw a diagram for this situation and then use the Law of Sines.

≈ 90.2 ft

Practice makes perfect

Let's recall that the Law of Sines relates the sine of each angle to the length of the opposite side. For any △ ABC, let the lengths of the sides opposite angles A, B, and C be a, b, and c, respectively.

By the Law of Sines, we can write the following equation. sin A/a=sin B/b=sin C/c

In our case, we know that a 125-foot redwood tree is leaning 20^(∘) off vertical. We want to calculate the length of the shadow if the angle the sunlight makes with the ground is 68^(∘). Let's create a diagram for this situation. Let x represent the length for which we are looking.

Note that the angle opposite to x is 180^(∘) minus the measures of the two other angles. 180^(∘)-70^(∘)-68^(∘)= 42^(∘) Let's add this information to our diagram.

Let's write the equation according to the Law of Sines, and then solve it!
sin 68^(∘)/125=sin 42^(∘)/x
sin 68^(∘)=sin 42^(∘)/x* 125
sin 68^(∘)=125sin 42^(∘)/x
sin 68^(∘) x=125sin 42^(∘)
x=125sin 42^(∘)/sin 68^(∘)
Finally, we will use a calculator to calculate the value of sines.
x=125sin 42^(∘)/sin 68^(∘)
x=90.2100757...
x≈ 90.2
The length of the shadow is about 90.2 feet.