由sinx>=-1/2
cosx>√ 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>=-1/2 你就画图,正弦曲线画出来后,值域大于等于-1/2,你就在图上找,并用笔深深地画出那段曲线,同理cosx>√ 2/2也一样,再就是x要满足这两个方程,取交集,你再画画看
由sinx>=-1/2
cosx>√ 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>=-1/2 你就画图,正弦曲线画出来后,值域大于等于-1/2,你就在图上找,并用笔深深地画出那段曲线,同理cosx>√ 2/2也一样,再就是x要满足这两个方程,取交集,你再画画看