sinx + cosx = 1/5 ==> cosx = 1/5 - sinxsin²x + cos²x = 1sin²x + (1/5 - sinx)² = 125sin²x - 5sinx - 12 = 0(5sinx - 4)(5sinx + 3) = 0sinx = 4/5 或 sinx = - 3/5因为0 < x < π,sin...