如何证明 tan^-1(x)-tan^-1(x-1/x+1)=π/4,x>-1?
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tan(tan^-1(x-1/谨兄碧x+1)+π/4)
=(tan(tan^-1(x-1/祥举x+1))+tan(π/4))/尘空(1-tan(tan^-1(x-1/x+1))tan(π/4))
=((x-1)/(x+1)+1)/(1-(x-1)/(x+1))
=x
故等式两边同时取tan^-1,有
tan^-1(x-1/x+1)+π/4=tan^-1(x)
即 tan^-1(x)-tan^-1(x-1/x+1)=π/4,
=(tan(tan^-1(x-1/祥举x+1))+tan(π/4))/尘空(1-tan(tan^-1(x-1/x+1))tan(π/4))
=((x-1)/(x+1)+1)/(1-(x-1)/(x+1))
=x
故等式两边同时取tan^-1,有
tan^-1(x-1/x+1)+π/4=tan^-1(x)
即 tan^-1(x)-tan^-1(x-1/x+1)=π/4,
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