In the triangle ABC, if a is less than B, less than C and C2 is less than A2 + B2, then the triangle ABC is

In the triangle ABC, if a is less than B, less than C and C2 is less than A2 + B2, then the triangle ABC is

COSC = (a ^ 2 + B ^ 2-C ^ 2) / 2Ab
Because C ^ 20 and ab > 0
So COSC > 0
So 0