1. The problem statement, all variables and given/known data is the author wrong ? i was told that the f(x) = 0.5(a_0) +Σ(a_n)cos (nπx / L ) ........ but , in the example(photo2) , the author ignore the L , which the author gave f(x) = 0.5(a_0) +Σ(a_n)cos (nπx ) +...... 2. Relevant equations 3. The attempt at a solution P/ s : i have tried to make some correction beside the working , is it correct ?