Matematika

Pertanyaan

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1 Jawaban

  • Tabung dalam Bola

    Jar jari tabung = r = x
    tinggi tabung =t =  2y
    x² + y²  = R²
    y² = R² - x²
    x² =R² - y²

    a) V tabung = π r² t = π (R²-y²)(2y)
    V tabung = 2 πy (R²-y²)

    b) t maksimum = ...
    t = 2y
    .
    V tab = 2 π y (R² - y²)
    V(y) = 2 π R²  y - 2 π y³
    V' (y)= 0 --> 2 π R² - 6 πy² = 0
    2πR² = 6 π y²
    R² = 3 y² --> y² = R²/3
    y = √(R²/3) = R/√3
    t = 2y -->
    t = 2R/√3

    .
    c. V tabung : V bola
    V tabung = π r² t
    Vtab = π (R²-y²)(2R/√3)
    V tab = π (R² - R²/3) (2R)(1/√3)
    V tab = π (2/3  R²)(2R)(1/3)(√3)
    V tab = π R³ (4/9)(√3)
    Vbola  = π R³ (4/3)
    .
    V tab : Vbola = (4/9)√3  : (4/3) =  (4√3) : (12) = √3 : 3 = 1 : √3