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    Sector of a circle centre O, angle (theta), and radius r cm. The parameter of the sector is 40cm and the area is A cm^2.
    1. Show that A = 100 - (r - 10)^2
    2. Given that r may vary, deduce the value of r for which A is a maximum.
    State the maximum value of A and find, in radians, the value of (theta) which maximises A.
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    (Original post by Maliha99)
    Sector of a circle centre O, angle (theta), and radius r cm. The parameter of the sector is 40cm and the area is A cm^2.
    1. Show that A = 100 - (r - 10)^2
    2. Given that r may vary, deduce the value of r for which A is a maximum.
    State the maximum value of A and find, in radians, the value of (theta) which maximises A.
    Well... what have you tried?
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    My daughter is stuck on this one. Ive set this up for her. Hope you can help please
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    (Original post by Maliha99)
    Sector of a circle centre O, angle (theta), and radius r cm. The parameter of the sector is 40cm and the area is A cm^2.
    1. Show that A = 100 - (r - 10)^2
    2. Given that r may vary, deduce the value of r for which A is a maximum.
    State the maximum value of A and find, in radians, the value of (theta) which maximises A.
    If you know that the perimeter is 40 cm, then r\theta + 2r= 40.

    A = \frac{1}{2}r^2 \theta - you want to get rid \theta - re-arrange the first equation and then substitute theta into the second one to eliminate it.
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    Thats great thanks. Could you help with part 2.
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    (Original post by Maliha99)
    Thats great thanks. Could you help with part 2.
    Solve \frac{dA}{dr} = 0.

    By the way, press the reply button on my post when you're replying to me so I get a notification.
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    Thanks alot for you kind help today.
    (Original post by Zacken)
    Solve \frac{dA}{dr} = 0.

    By the way, press the reply button on my post when you're replying to me so I get a notification.
 
 
 
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