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


Sagot :

Answer:

Step-by-step explanation:

That will be a square with a diagonal of 20

side length of 20sin45

and area of (20sin45)² = 200 units²

prove it you say?

Area of a rectangle is base times height

A = bh

With a radius of 10, the diagonals of any rectangle inscribed will be 20 units

20² = b² + h²

h = [tex]\sqrt{400 - b^2}[/tex]

A = bh

A = b[tex]\sqrt{400 - b^2}[/tex]

Area will be maximized when the derivative is set to zero

           dA/db = [tex]\sqrt{400 - b^2}[/tex] - b²/ [tex]\sqrt{400 - b^2}[/tex]

                   0 = [tex]\sqrt{400 - b^2}[/tex] - b²/ [tex]\sqrt{400 - b^2}[/tex]

b²/[tex]\sqrt{400 - b^2}[/tex] =  [tex]\sqrt{400 - b^2}[/tex]

                  b² = 400 - b²

                2b² = 400

                  b² = 200

                  b = [tex]\sqrt{200}[/tex]

h = [tex]\sqrt{400 - b^2}[/tex]

h = [tex]\sqrt{400 - \sqrt{200}^2 }[/tex]

h = [tex]\sqrt{200}[/tex]

A = bh

A =  [tex]\sqrt{200}[/tex][tex]\sqrt{200}[/tex]

A = 200 units²