Which of the following is a key element in the proof of the law of cosines?
Athe triangle inequality theorem
BAngle A+ Angle B+ Angle=180
CA=1/2b*h
Dd=square root of (x^2+x^1)+(y^2-y^1)^2
Athe triangle inequality theorem
BAngle A+ Angle B+ Angle=180
CA=1/2b*h
Dd=square root of (x^2+x^1)+(y^2-y^1)^2