不会做啦，有没会数学的帮帮我啊

(1)
2 tan x = cos x ,
2 sin x / cos x = cos x ,
2 sin x = cos^2 x = 1 - sin^2 x ,
sin^2 x + 2 sin x - 1 = 0 ,
( sin x + 1 )^2 = 2 ,
sin x + 1 = ± √2 ,
sin x = - 1 ± √2 ,
因为 - 1 ≤ sin x ≤ 1 ,
所以 sin x = √2 - 1 .
所以 x = 2 k π + arcsin (√2 - 1)
或 x = 2 k π + π - arcsin (√2 - 1) , ( k ∈ Z ) .
(2)
sin x = tan x ,
sin x = sin x / cos x ,
所以 sin x = 0 ,或 cos x = 1 ,
所以 sin x = 0 ,
所以 x = k π ( k ∈ Z ) .
(3)
解法一：
2 sin^2 x = 1 ,
sin^2 x = 1 / 2 ,
sin x = ± √2 / 2 ,
所以 x = k π / 2 + π / 4 ,( k ∈ Z ) .
解法二：
2 sin^2 x = 1 ,
1 - 2 sin^2 x = cos (2 x) = 0 ,
所以 2 x = k π + π / 2 ,
所以 x = k π / 2 + π / 4 ,( k ∈ Z ) .

题目出错了吧