41 lines
1.0 KiB
Python
41 lines
1.0 KiB
Python
import math
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#把函数改成题干的形式#####################
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def f(x):
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return x**2 - 30
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def df(x):
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return 2*x
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# 牛顿方法求解方程
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def NewtonSolve(fx, dfx, x0, err, N0):
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count = 0
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print(f"k={count}, x0={x0}")
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x1 = x0 + 1 + err
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while abs(x1 - x0) > err or abs(fx(x1)) > err: # 添加条件修正根误差太大的问题
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if abs(dfx(x1)) < 1e-10:
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return None, 0
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x1 = x0 - fx(x0) / dfx(x0)
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count += 1
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print(f"k={count}, x{count}={x1},x1-x0={abs(x1-x0)}")
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if count > N0:
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return None, -1
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x0 = x1
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return x1, 1
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# 查找根区间
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def FindRootZone(fx,start,stop,step):
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x = start
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while x < stop:
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if fx(x) * fx(x+step) < 0:
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return x
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x += step
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return None
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if __name__ == "__main__":
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err = 1e-4
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N0 = 100
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x0 = FindRootZone(f, 5, 6, 0.1) # 查找f的根的区间与步长，改成题干对应的范围
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result,status = NewtonSolve(f, df, x0, err,N0)
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print(f"sqrt(30) = {result:.3f}") |