由sinx＞=-1/2cosx>√ 2/2可得：2πn-(π/6)＜= x ＜＝2πn+(7π/6)2πn-(π/4)＜x＜2πn+(π/4)(n取整数)联立解得：2πn-(π/6)＜= x ＜2πn+(π/4) (n取整数)多画图,自然就知道了 sinx＞=...