Radians Watch

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Bengaltiger
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#1
Report Thread starter 13 years ago
#1
Ive attached the question. I need help on bi. I dont understand what i have to do.
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seankhn
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#2
Report 13 years ago
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Well the area of a sector is a fraction of the area of a circle that is proportional to the angle in the middle.

i.e. if the angle in the middle is 2pi, (pi)(r)^2 = 2pi/2pi * (pi)(r)^2

if the angle were π/16 the area would be π/16 * (pi)(r)^2

For part b, do da/dr to get the differential and hence the maximum

show it by d²a/dr²

For the next bit you have to insert the value you just got for max r into a formula containing the angle then rearrange to find the max area angle

to get the max area of sector, insert the values from max r back into A = 50r - r²
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Bengaltiger
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#3
Report Thread starter 13 years ago
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Thanks for that. Never thought about differntiating it. The book is so wiered cause the differentiation chapter is after the radians.....
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