由题可知：$$B=\left { 1,4,\frac{1}{4} \right }$$，所以 $$A\cap B=\left {1 \right }$$． 
已知集合$$A=\left { 1,2,\frac{1}{2} \right }$$，集合$$B=\left { y\left\textbar{} y={{x}^{2}},x\in A \right. \right }$$，则$$A\cap B=$$（~ ~）．
Options:
* $$\left { \frac{1}{2}\right }$$ 
* $$\left { 2 \right }$$ 
* $$\left { 1 \right }$$ 
* $$\varnothing $$ 