Saturday, November 21, 2009

Fox 189


1 comment:

  1. Answer is E.

    Similar notation that Fox 7, we have:

    A=Area
    x=AO, y=BO

    A = xy/2 = 2/sin(2alpha) -> A'(alpha)=0 ->

    -> A'(alpha) = -4cos(2alpha)/sen^2(2alpha) = 0 -> alpha = pi/4 -> A(pi/4)= 2 is minimum area of tr. AOB.

    Note: Second derivative A''(alpha) is positive at alpha = pi/4.

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