✔ 最佳答案
x, y, z 成等差數列 (單位為 cm)
設 a 及 d (d > 0) 分別是該等差級數的第一項和公差。
x = a
y = a + d
z = a + 2d
該三角形的周界:
x + y + z = 42
a + (a + d) + (a + 2d) = 42
3a + 3d = 42
a + d = 14
a = 14 - d ...... (1)
該三角形是直角三角形,根據畢氏定律:
x2 + y2 = z2
a2 + (a + d)2 = (a + 2d)2
a2 + a2 + 2ad + d2 = a2 + 4ad + 4d2
a2 - 2ad - 3d2 = 0
(a - 3d)(a + d) = 0
a = 3d 或或或 a = -d (捨棄,因 a 和 d 均為正數)
a = 3d ...... (2)
(2) = (1):
3d = 14 - d
4d = 14
d = 3.5
(2):
a = 3(3.5)
a = 10.5
x = a = 10.5
y = a + d = 10.5 + 3.5 = 14
z = a + 2d = 10.5 + 2(3.5) = 17.5
答:三角形的邊長分別是 10.5 cm, 14 cm 和 17.5 cm。
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