additional maths

The area, A cm3 , of a circle increases at a constant rate of 2 cm2 ´ s -1 . If the initial area of A is 1 cm2 , show that the radius of the circle at time t is given by r=sqrt( 2t+1/ pi) sqrt on both denominator and numerator

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  1. I don't know if you are the same person, but this question is a cut-and-past of
    http://www.jiskha.com/display.cgi?id=1422453360

    areas are measured in cm^2 , not cm^3
    I cannot understand 2 cm2 ´ s -1

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  2. we know that
    dA/dt = 2
    and A can be written as pi*r^2

    inital value of A, meaning t=0, is 1
    from that, we get the equation
    A = 2t+1

    example:
    t = 2
    A = 2(2) + 1 = 5
    1 + 2 + 2 = 5

    we can then write
    pi*r^2 = 2t + 1
    r^2 = 2t + 1/pi
    r = sqrt. 2t+1/pi

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