Question

If vector r =a-b show that r^2=a^2+b^2-2abcos(x)

Answer 1

R^2=A^2+B^2+2ABCosX

|A|=|B|

R^2=A^2+A^2+2AACosX

R^2=2A^2+2A^2CosX

R^2=2A^2(1+CosX)

R=√{2A^2(1+CosX)

Or

By doing same above

R=√{2B^2(1+CosX).