f ( x ) = x * 2 y -> max.
Nebenbedingung (Länge der Laufbahn):
2 x + 2 π y = 400
<=> y = ( 400 - 2 x ) / 2 π = ( 200 - x ) / π
Einsetzen in f ( x ) :
f ( x ) = x * 2 * ( ( 200 - x ) / π )
= ( 400 x - 2 x 2 ) / π
f ' ( x ) = ( 400 - 4 x ) / π = 0
<=> ( 400 - 4 x ) / π = 0
<=> 400 - 4 x = 0
<=> x = 100
=> y = ( 200 - 100 ) / π ≈31,83 m
fmax = x * 2 y = 100 * 63,66 = 6366 m 2