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Thread: geometry help.

  1. #1

    geometry help.

    my math program gave me a question i thought i knew how to answer, but i keep getting it wrong, and nobody can tell me what im doing wrong.

    in an equilateral triangle where all sides = 7, find the area.

    so i cut it in half, so A = 3.5 and C =7. so, the squares are 12.25 and 49.

    to find B, i did 49 - 12.25 = 36.75 , and then got the square root of that, 6.062. so, that is the hight of the triangle. 7 * 6.062 is 42.434. half of that is 21.217.

    i put that as the answer, but got it wrong, nobody can explain to me why, ive tried rounding it to 21, 21.2, and 21.22..and none of those helped. can somebody help me with a different way of doing this, or tell me what im doing wrong?

  2. #2

    Re:geometry help.

    hello,
    i think you are thinking of pathagorian formula - to get the length of the hypotnynse for a right triangle, the fomula for the area of a trianle is l*h*1/2 - which in this case would be 24 1/2

  3. #3
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    Re:geometry help.

    I get exactly the same answer as you TeRG. PBharris, you are right about the formula, however as it is an equilateral triangle, 7 is not the height. If each side of the triangle has length 7, the there is no way the height can be 7 as they are angled inwards. So if you cut the triangle into two right angled triangles, with base 3.5 and hypotenuse 7, then you get the height of the triangle.
    CP

  4. #4

    Re:geometry help.

    i will have to ask for help tommorow, though we dont have a "math teacher" the system administrater knows his math inside and out. maybe he will have something to say.

    and CP, so do you think my approach to the problem was the proper way? or do you think im off by something?

  5. #5
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    Re:geometry help.

    I did it exactly the same way as you TeRG. I have no idea why that isn't the correct answer.

  6. #6

    Re:geometry help.

    ok. i got it. the program wanted 21.20. though i dont see why 21.2 wasnt good enough.

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    By TeRG in forum General Chat
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