Muhd Ilman Fahmi's answer to Shion's Junior College 1 H1 Maths question.
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Pardon the handwriting
You first start off with the area of a circle equation, A = pi × r^2, and then differentiate to get dA/dr
You are given rate of change of area, dA/dt, and using chain rule you can get dr/dt.
You can find the equation of r in terms of t or otherwise, in order to get the value of r at any given t, such like for part ii. (Bottom left)
With that, you can substitute any value of r to get the rate of change of radius over time.
Give it a try! Hope it helps
You first start off with the area of a circle equation, A = pi × r^2, and then differentiate to get dA/dr
You are given rate of change of area, dA/dt, and using chain rule you can get dr/dt.
You can find the equation of r in terms of t or otherwise, in order to get the value of r at any given t, such like for part ii. (Bottom left)
With that, you can substitute any value of r to get the rate of change of radius over time.
Give it a try! Hope it helps
Date Posted:
7 years ago
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