Hi MHF!

I've been here asking some simple questions about geometry before.

Now, I'm having a lot of difficulty regarding maximization of area.

The thing I don't know is,how to get the formula of the area to be maximized.

Here are two problems

https://lh5.googleusercontent.com/_j...e10%20copy.gif

(MHF is not helping at all, I can't seem to upload anything here!)

This first problem asks to maximize the area of the rectangle, and to give the measure of the maximized triangle.

The other one

https://lh3.googleusercontent.com/_j...his%20copy.gif

Asks to maximize the are of the quadrilateral ABCD.

The point D is in the minor arc AC.

Can someone help me?

The main problem here is, how to get the area of the thing to be maximized?

Thanks!!