2sec^2 x-5tanx+1=0
2(tan^2x+1)-5tanx+1=0
2tan^2x-5tanx+3=0
(2tanx-3)(tanx-1)=0
tanx=3/2 tanx=1
所以x=kπ+arctan3/2 或者x=kπ+π/4
解方程 2sec^x-5tanx+1=0
2sec^2 x-5tanx+1=0
2(tan^2x+1)-5tanx+1=0
2tan^2x-5tanx+3=0
(2tanx-3)(tanx-1)=0
tanx=3/2 tanx=1
所以x=kπ+arctan3/2 或者x=kπ+π/4