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  • May 15, 2008, 11:09 AM
    henna_naz
    Trigonometry quadratic equation
    Can you please help me on this, I have just seen that somebody else has asked this question previously but I don't understand how you manage to get two lengths.

    Trigonometric Question:-
    In triangle ABC, the angle A is 42 degrees, the side AB is 16cm and the side BC is 14cm. Find the two possible values of the side AC. How do you get two lengths?
  • May 16, 2008, 02:31 PM
    ebaines
    1 Attachment(s)
    One way to solve this is to use the law of cosines, which states:



    Here you can substitute 16 for length A, 14 for length C and 42 degrees for angle C, and solve for length B. Because it's a quadratic equation, you'll get two values for length B. See the attached figure and you'll see how that works - the third side of the triangle can be either BC or BC'.

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