sinx + cosx/√3
= sinx + √3/3 * cosx
= (2/√3) ( √3/2 * sinx + 1/2 cosx)
= (2/√3) (cos30 sinx + sin30 cosx)
= (2/√3) sin(x + 30)
即 sin(x + 30) = √3/2
x = 2kπ + π/6 或 x = 2kπ + π/2
其中 2/√3 = √[1² + (√3/3)²]