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The distance between you and your friend is changing at a rate of 20 miles per hour.
What is the Pythagorean theorem?
A right triangle's three sides are related in Euclidean geometry by the Pythagorean theorem, also known as Pythagoras' theorem. According to this statement, the areas of the squares on the other two sides add up to the size of the square whose side is the hypotenuse.
Here, we
Let the east direction is denoted by x and
the north direction is denoted by y.
dx / dt = 16 miles per hour
dy / dt = 12 miles per hour
x = 4 miles
Let the distance between both the friends be s.
Time is taken by you to travel 4 miles,
time = distance / speed = 4 / 12 = 1/4 hour
Distance traveled by your friend in time t,
y = speed x time = 12 x 1/4 = 3 miles
By Using the Pythagorean theorem,
x² + y² = s² ..... (1)
Substitute, x = 4 mile, y = 3 mile
s² = 16 + 9 = 25
s = 5 miles
Now, Differentiate equation (1) with respect to t, we get
2x dx/dt + 2y dy/dt = 2s ds/dt
4 (16) + 3 (12) = 5 ds/dt
ds/dt = 20 miles per hour
Hence, the distance between you and your friend is changing at a rate of 20 miles per hour.
To learn more about the Pythagorean theorem from the given link
https://brainly.com/question/16176867
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