(

x

x+1

+1)÷(1-

3x2

1-x2

)•

1

x-1

=

2x+1

x+1

÷

1-4x2

1-x2

•

1

x-1

=

2x+1

x+1

•

(1+x)(1-x)

(1+2x)(1-2x)

•

1

x-1

=

1

2x-1

，

∵x=

3

sin45°•cot60°=

3

×

2

2

×

3

3

=

2

2

，

∴原式

1

2× 2 2 -1

=

1

2 -1

=

2

+1．