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Homework Help: Partial derivations

  1. Oct 9, 2005 #1
    I have a problem and I am stuck to one question:

    The area of a triangle is given by the formula: A=1/2*b*c*sin(θ )

    At time to, we have bo=10 inches, co=20inches, θo=pi/3

    a) Find the area of the triangle at to
    I found 50*sqrt(3)

    b- find the rate of change of the area with respect to b at to.
    I found 5*sqrt(3).

    c) Find the rate of change of the area with respect with θ at to.
    I found 50.

    d) Using the rate found in part c) , calculate (by differentials) the approximate change in area if angle theta is increased by one degree.
    I need help for this question. I do not know what to do here.

    Thank you for your help
  2. jcsd
  3. Oct 9, 2005 #2


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    Homework Helper

    I'm guessing that b is the hypotenuse and c is the leg
    that adjoins the angle theta.

    I notice that you have ignored the UNITS of these...
    units are our friends, and keep us in the right dimension.

    As the angle increases, b increases in length and the sine of theta increases.
    Both of these will increase the area of the triangle.
    When you find out how MUCH, it will have units: in^2 .
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