It is known that ABC is the length of three sides of a triangle. Try to compare the size of a square + b square + C square and 2BC

It is known that ABC is the length of three sides of a triangle. Try to compare the size of a square + b square + C square and 2BC

The proof of the former big a ^ 2 + B ^ 2 > equals to 2Ab a ^ 2 + B ^ 2 > C ^ 2