△ABC中,a²≤b²+c²-bc,则A的取值范围是?A.π/6 B.π/3 C.2π/3 D.5π/6
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![△ABC中,a²≤b²+c²-bc,则A的取值范围是?A.π/6 B.π/3 C.2π/3 D.5π/6](/uploads/image/z/12888257-41-7.jpg?t=%E2%96%B3ABC%E4%B8%AD%2Ca%26%23178%3B%E2%89%A4b%26%23178%3B%2Bc%26%23178%3B-bc%2C%E5%88%99A%E7%9A%84%E5%8F%96%E5%80%BC%E8%8C%83%E5%9B%B4%E6%98%AF%3FA.%CF%80%2F6+B.%CF%80%2F3+C.2%CF%80%2F3+D.5%CF%80%2F6)
△ABC中,a²≤b²+c²-bc,则A的取值范围是?A.π/6 B.π/3 C.2π/3 D.5π/6
△ABC中,a²≤b²+c²-bc,则A的取值范围是?A.π/6 B.π/3 C.2π/3 D.5π/6
△ABC中,a²≤b²+c²-bc,则A的取值范围是?A.π/6 B.π/3 C.2π/3 D.5π/6
b^2+c^2-a^2>=bc
COS A=(b^2+c^2-a^2)/2bc>=1/2
所以A取值(0,π/3 ] [2π/3 ,π)