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secondary 4 | A Maths
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Ans is 1/12 but I got 16(pie)r
Date Posted: 5 years ago
Views: 219
dA/dt = 8cm²/s
Area of circle, A = πr²
dA/dr = 2πr
dr/dt = dA/dt x dr/dA
= dA/dt ÷ dA/dr
= 8 ÷ 2πr
Since circumference = 96cm and we know that circumference = 2πr,
dr/dt = 8cm²/s ÷ 96cm = 1/12 cm/s
Area of circle, A = πr²
dA/dr = 2πr
dr/dt = dA/dt x dr/dA
= dA/dt ÷ dA/dr
= 8 ÷ 2πr
Since circumference = 96cm and we know that circumference = 2πr,
dr/dt = 8cm²/s ÷ 96cm = 1/12 cm/s
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We are given the circumference of the circle. We must extract the radius out of this data.
Subsequently, we define the area of the circle and then evaluate dA/dr when r = the radius which you obtained earlier.
You are also given that dA/dt.
By the chain rule,
dA/dt = dA/dr * dr/dt
Sub in values of dA/dt and dA/dr.
Subsequently, we define the area of the circle and then evaluate dA/dr when r = the radius which you obtained earlier.
You are also given that dA/dt.
By the chain rule,
dA/dt = dA/dr * dr/dt
Sub in values of dA/dt and dA/dr.
Date Posted:
5 years ago
Sorry, dr/dt = 1/12 cm/s. Correction.
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