Exercise 41 To measure the width of a river, you plant a stake on one side of the river, directly across from a boulder.
You then walk 100 meters to the right of the stake and measure a 79° angle between the stake and the
boulder. What is the width w of the river? Round your answer to the nearest meter.
Mattraimale
079
100 m
PUR
m

514 m = width of the river to the nearest meter

Step-by-step explanation:

You must memorize the definitions of the trig functions and then these types of problems are easy.

You have a right triangle where the 100 m is the adjacent side to the 79° angle.  You are looking for the side opposite the 79° angle.  So, you need to use the tan function which is defined as opposite side/adjacent side

Let x = the length of the opposite side (width of river)

Tan 79 = x/100

100 tan 79 = x

x = 514 m = width of the river to the nearest meter

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