y=√[2cos(2x-1)]
cos(2x-1)≥0,
所以2kπ-π/2≤2x-1≤2kπ+π/2.
解得kπ-π/4+1/2≤x≤kπ+π/4+1/2,定义域为[kπ-π/4+1/2,kπ+π/4+1/2],k∈Z.