Question

The angle between two vectors a 3i+4j+5k and b=3i+4j-5k will be

Answer 1

90°

α be the angle

cosα=a.b/ΙaΙ ΙbΙ

      =(3i+4j+5k)(3i+4j-5k)/√3²+4²+5²√3²+4²+5²

      =[3²+4²+(-5)5] / (√9+16+25)²

     =(9+16-25) / (9+16+25)

    =0/50 = 0

α=cos⁻¹0 =