
这个极限等于多少
2个回答
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let
y=x-1
lim(x->1) { tan[(π/4)x] -1 }/ (x-1)
=lim(y->0) { tan[(π/4)y-π/4 ] -1 }/y
=lim(y->0) { ( tan[(π/4)y] -1 )/( 1+tan[(π/4)y]) -1 }/y
=lim(y->0) 2tan[(π/4)y]/ { y. [ 1+tan[(π/4)y] }
=lim(y->0) 2tan[(π/4)y]/ y
=2(π/4)
=π/2
y=x-1
lim(x->1) { tan[(π/4)x] -1 }/ (x-1)
=lim(y->0) { tan[(π/4)y-π/4 ] -1 }/y
=lim(y->0) { ( tan[(π/4)y] -1 )/( 1+tan[(π/4)y]) -1 }/y
=lim(y->0) 2tan[(π/4)y]/ { y. [ 1+tan[(π/4)y] }
=lim(y->0) 2tan[(π/4)y]/ y
=2(π/4)
=π/2
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