Maximisation (1 Viewer)

[nahi11]

Hi,


Can anyone please help me with this question.



For (a)

I get A = pi*r^2 + pi(k - r)^2

For (b) I get
A'=2pi * (2r-k)
Therefore r= k/2

After that I know I am supposed to test either using the table or double differentiation but I seem to get stuck.

Thanks

 

[Carrotsticks]

Find the double derivative, which is 4pi. However, this is a constant greater than zero, so the stationary point is a minimum.

Hence r=k/2 yields a minimum.

Therefore 2r = k, implying that r_1 = r_2. It follows that the two circles are congruent.

 

[nahi11]

Lol damm I knew it.

Thanks! REp+