[填空题]
A function is defined 4cml)in ) ff4hs(;yxwbu 4qfy,-qd,jjkhzmu+1rak:4 8 n7 oin y f(x)=a cos (k x)+c , for $-\pi \leq x \leq \pi $, where k>0 . Part of the graph of y=f(x) is shown on the diagram below.
1. Find the value of:
1. a ;
2. k ;
3. c .
2. Solve f(x)=2 , for 0$ \leq x \leq \pi$ .
