find the dimensions of a rectangle with maximum area that can be inscribed in a circle of radius 10

Question

anonymous · Answer

attachment

anonymous · Answer

First of all, for the record, the rectangle is going to, well, be a square. 

Now to the actual math. First, notice that the circle's diameter (which is 20) is the diagonal of the square. Now, a square's side is equal to its diagonal divided by the square root of 2. 

20 / sq-rt(2) = 20sq-rt(2) / 2 = 10 times the square root of 2, or about 14.

anonymous · Answer

I dont understand. From the attachment I understand everything until the derivative and i underlined/pointed to the specific part that im confused with

linknissan · Answer

hello! i can help you with the solution PM me..

anonymous · Answer

ummm i got this answer from yahoo answers but i think it is 200

anonymous · Answer

@linknissan I did! :D

doc.brown · Answer

I would have found
$$x=d\cos\theta$$$$20\cos(45)$$$$x=14.14$$$$A=14.14^2$$$$A=200$$