Question: The diagram shows a window made from a rectangle with base 2r m and height h m and a semicircle of radius r m. The
The diagram shows a window made from a rectangle with base 2r m and height h m and a semicircle of radius r m. The perimeter of the window is 6 m and the surface area is A m2.
a. Express h in terms of r.
b. Show that A = 6r – 2r2 – ½ πr2.
c. Find dA/dr and d2A/dr2.
d. Find the value for r for which there is a stationary value of A.
e. Determine the magnitude and nature of this stationary value.

rm hm 2rm
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a h 2 r b A 6 r 2 r 2 r 2 c d A dr 6 4 r r d 2 A dr 2 4 d The value for r for which there is a stati... View full answer
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