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# Math help!!! watch

1. 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.
2. (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?
3. My daughter is stuck on this one. Ive set this up for her. Hope you can help please
4. (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 .

A = - you want to get rid - re-arrange the first equation and then substitute theta into the second one to eliminate it.
5. Thats great thanks. Could you help with part 2.
6. (Original post by Maliha99)
Thats great thanks. Could you help with part 2.
Solve .

By the way, press the reply button on my post when you're replying to me so I get a notification.
7. Thanks alot for you kind help today.
(Original post by Zacken)
Solve .

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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