Smile 發問於 科學及數學數學 · 1 年前

Maths problem, thanks?

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6 個解答

評分
  • 1 年前
    最愛解答

    △ABC : △ADE = AC : AE

    △ABC : 1 = (AC/AD) : (AE/AD)

    △ABC = (1/cos60°) : cos60°

    △ABC = 2 : 1/2

    △ABC = 4 cm²

    The answer is B.

  • SC147
    Lv 6
    1 年前

    ∠B=∠E=90⁰

    ∠BAC=30⁰=∠EDA

    ∠BCA=60⁰=∠EAD

    ∴ △ABC ~ △DEA (AAA)

    => area of △ABC :area of △DEA =AC² :DA²

    => area of △ABC :1 = AC² :DA²

    => area of △ABC = (AC/DA)² . . . . . . . . . . . . . . . ①

                   DA

    From rt-angled △ADC, cos 60⁰ = ------

                   AC

                 ½ = DA/AC

             

    From ①: area of △ABC = (2/1)² = 4  (ans : B )

  • △ABC : △ADE = AC : AE 

    △ABC : 1 = (AC/AD) : (AE/AD) 

    △ABC = (1/cos60°) : cos60° 

    △ABC = 2 : 1/2 

    △ABC = 4 cm² 

    The answer is B

  • 1 年前

    △ABC : △ADE = AC : AE

    △ABC : 1 = (AC/AD) : (AE/AD)

    △ABC = (1/cos60°) : cos60°

    △ABC = 2 : 1/2

    △ABC = 4 cm²

    The answer is B.

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  • 1 年前

    △ADE ~ △CAB

    area△ADE : area△ABC = AD ² : AC ² = 1² : 2² = 1 : 4

    4cm²

    B. #

  • 匿名
    8 月前

    The answer is B

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