If A ={a,b,c,d} and the function f={(a,b),(b,d),(c,a),(d,c)}, write f−1.
By definition of inverse function, if f(x)=y, then f−1(y)=x Given that, A={a,b,c,d} and f={(a,b),(b,d),(c,a),(d,c)} ∴f−1={(b,a),(d,b),(a,c),(c,d)}
In figure, AB ∥ DE, AB = DE, AC ∥ DF and AC = DF. Then, BC ∥ EF and BC = ___ .