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Understanding this formula: area = 0.5 a * b * sinc watch

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    I'm assuming this is correct:
    C is the angle between the sides a and b
    B is the angle between the sides a and c
    A is the angle between the sides c and b

    Here is the problem: The area of the triangle is 100cm^2
    http://imageshack.us/photo/my-images/17/triangle3.jpg/

    I have to find angle ABC

    formula: Area = 0.5 * a * b * sin(c)
    so 100cm^2 = 0.5 * AB * AC * sin(BAC)
    so 100cm^2 = 0.5 * 16cm * 16cm * SIN(BAC)
    So angle BAC = 51.375

    So ABC should be (180-51.375)/2 = 64.1
    but the book says ABC = 51.4..
    Does the formula not work for an isosceles?
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    (Original post by Bobby132)
    I'm assuming this is correct:
    C is the angle between the sides a and b
    B is the angle between the sides a and c
    A is the angle between the sides c and b

    Here is the problem: The area of the triangle is 100cm^2
    http://imageshack.us/photo/my-images/17/triangle3.jpg/

    I have to find angle ABC

    formula: Area = 0.5 * a * b * sin(c)
    so 100cm^2 = 0.5 * AB * AC * sin(BAC)
    so 100cm^2 = 0.5 * 16cm * 16cm * SIN(BAC)
    So angle BAC = 51.375

    So ABC should be (180-51.375)/2 = 64.1
    but the book says ABC = 51.4..
    Does the formula not work for an isosceles?
    the formula works for all triangles, there could be an error in your book
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    Your triangle is not labelled properly. This is how you should label it.

    You can check that the above information agrees.
 
 
 
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