Unprotect
 Usage
• Unprotect[ ,  , ... ] 对符号  去掉属性 Protected。 • Unprotect[" ", " ", ... ] 不对它们的名字匹配任何  的所有符号进行保护。
Notes
• 在对内嵌函数加入你自己的规则时，一个典型序列是 Unprotect[f]; definition; Protect[f]。
 Further Examples
Logs of products are not automatically broken up into a sum of logs.
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After unprotecting Log we can define a new transformation rule.
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We apply the rule and then get rid of it, reprotect the Log function.
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The Clear did not get rid of system definitions.
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