If `veca` and `vecb` are unit vectors inclined at an angle `theta`,then prove that `sin(theta/2)=1/2|veca-vecb| `

If veca, vecb, vecc are unit vectors then, veca.veca =_____

If veca,vecb,veca+vecb are unit vectors, then prove that the angle between veca and vecb is (2pi)/(3)

Let 'veca' and 'vecb' be two unit vectors and 'theta' is the angle between them. Then 'veca,+vecb' is a unit vector if

For any three vectors veca,vecb and vecc , and, prove that (veca+vecb)+vecc=veca+(vecb+vecc) .