(a) If A is the area of a circle with radius r and the circle expands as time passes, find dA dt in terms of dr dt . dA dt

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If A is the area of a circle with radius r and the circle expands as time passes, find dA/dt in terms of dr/dt. dA dt = dr dt (b) Suppose oil spills from a ruptured tanker and spreads in a circular pattern. If the radius of the oil spill increases at a constant rate of 1 m/s, how fast is the area of the spill increasing when the radius is 25 m?

Area of the circle A = πr²

dA/dr = 2πr where r is the radius of the circle

dA/dt = dA/dr * dr/dt

dr/dt is the rate of increase in radius of the oil spill.

Given

dr/dt = 1m/s

radius r = 25m

Substitute into the formula above;

dA/dt = dA/dr * dr/dt

dA/dt = 2πr * 1

dA/dt = 2π(25) * 1

dA/dt = 50πm²/s

dA/dt = 157.1m²/s

Hence the area of the spill is increasing at the rate of 157.1m²/s