问题描述:
你刚刚答的那道题我没看懂
cos[(π/4+α)-(π/4-α)]为什么=cos(π/4+α)cos(π/4-α)+sin(π/4+α)sin(π/4-α)
cos[(π/4+α)-(π/4-α)]为什么=cos(π/4+α)cos(π/4-α)+sin(π/4+α)sin(π/4-α)
问题解答:
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