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Math Help - need a formula for triangle

  1. #1
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    Exclamation need a formula for triangle

    hi i need to find the angle theta that maximizes the area of the isosceles triangle with legs length L. Once I can get a formula, I am fine to calculate the derivatives and determine the maximum, but my trig is a little rusty, especially with angles.
    I need to know how to find the formula to express the area in terms of the angle, theta (theta is between the two identical sides of the isosceles).

    thanks
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  2. #2
    Super Member wingless's Avatar
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    If length of two identical sides is L and the angle between them is θ, the area is A = \frac {1}{2} L^2 sin(\theta)
    Last edited by wingless; December 6th 2007 at 07:24 AM. Reason: typing errors
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  3. #3
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    alright, so next question

    if i use the formula above to express area and take the derivative of said formula, will the derivative be cos(theta)? do I treat L as a constant?
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by lostderiv View Post
    if i use the formula above to express area and take the derivative of said formula, will the derivative be cos(theta)? do I treat L as a constant?
    Quote Originally Posted by lostderiv View Post
    hi i need to find the angle theta that maximizes the area of the isosceles triangle with legs length L.
    That seems to be the problem you posted, so I would say yes.

    -Dan
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