Answer:
![a=√(170)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/i0li0csruhvzgaedxdcjauqlkykv6xipom.png)
Explanation:
Diagonal of a Square
Given a square of length side a, the length of the diagonal is
![D=√(2)a](https://img.qammunity.org/2020/formulas/mathematics/middle-school/n5zu90fc8jtf39epzwrtbj9hdj0fsa6qq2.png)
The diagonal of a rectangle of sides x and y is
![D=√(x^2+y^2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/f4rflcxqlifo0hzwiz2zfwaez8r5d655i6.png)
The sides have lengths 12 cm and 14 cm, the diagonal is
![D=√(12^2+14^2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jg73liuq2gip8t7q7srbpgifrxdae498sn.png)
![D=√(340)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/avuert8rupsrlrv58jrgttz9q4m8tinp9o.png)
Since this value is the same of the diagonal of certain square, we can say
![√(2)a=√(340)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ujdrurt7pm2hpuo31ntc7dv75o7irbgz9c.png)
Dividing by
![√(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/t462m14cxkj26cw9cmocfpgj44y1v8li5n.png)
![\boxed{a=√(170)}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mnhms4j0slfe3iyfpq5qx201s397l328ap.png)