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1 # xiong3506
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2 # warren吳
(sinx)"=cosx=sin(x+π/2)
(sinx)""=[sin(x+π/2)]"
=cos[x+(π/2)]=sin[x+2(π/2)]
…………
(sinx)^(n)=[sin(x+(n-1)(π/2))]"
=cos[x+(n-1)(π/2)]
=sin[x+n(π/2)]
(sinx)"=cosx=sin(x+π/2)
(sinx)""=[sin(x+π/2)]"
=cos[x+(π/2)]=sin[x+2(π/2)]
…………
(sinx)^(n)=[sin(x+(n-1)(π/2))]"
=cos[x+(n-1)(π/2)]
=sin[x+n(π/2)]
sinx)'=cosx=sin(x+π/2)
(sinx)''=[sin(x+π/2)]'=cos[x+(π/2)]=sin[x+2(π/2)]
(sinx)^(n)=[sin(x+(n-1)(π/2))]'=cos[x+(n-1)(π/2)]=sin[x+n(π/2)]
故sinx的n+1階導數是
(sinx)^(n+1)=sin[x+(n+1)(π/2)]。