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Math Help - perimeter very easy

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    Cool perimeter very easy

    There's a square drawn here and it's diagonal is shown as being 6sqrt3 cm long
    and i have to find the perimeter..how do i do this?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by kri999 View Post
    There's a square drawn here and it's diagonal is shown as being 6sqrt3 cm long
    and i have to find the perimeter..how do i do this?
    let the side length be x.

    then by Pythagoras' theorem, x^2 + x^2 = (6 \sqrt{3})^2 = 108

    solve for x. then the perimeter is given by 4x
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    oh yes sorry i forgot to mention that i have to use the rule about 45 45 90 triangles with this problem
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by kri999 View Post
    oh yes sorry i forgot to mention that i have to use the rule about 45 45 90 triangles with this problem
    why? that would only make your life harder. then you'd have to use sine or cosine or tangent or something

    if you insist, you could do \sin 45 = \frac x{6 \sqrt{3}} and solve for x from that
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    Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

    That's all i don't understand
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  6. #6
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    Quote Originally Posted by kri999 View Post
    Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

    That's all i don't understand
    Well x = \frac{6 \sqrt{3}}{\sqrt{2}} = \frac{6 \sqrt{3} \sqrt{2}}{\sqrt{2} \sqrt{2}} = \frac{6 \sqrt{6}}{2} = 3 \sqrt{6}.

    And the perimeter is equal to 4x.

    Therefore ......
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by kri999 View Post
    Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

    That's all i don't understand
    it would be good if you told us your difficulty. if you have trouble setting up the sine, cosine and tangent trig ratios, say so, and we can address it. if your problem was the algebra, then Mr. Fantastic already addressed that. do you understand the problem now? or is there something else?
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