The base of the pyramid `A O B C` is an equilateral triangle `O B C` with each side equal to `4sqrt(2),O` is the origin of reference, `A O` is perpendicualar to the plane of ` O B C` and `| vec A O|=2.` Then find the cosine of the angle between the skew straight lines, one passing though `A` and the midpoint of `O Ba n d` the other passing through `O` and the mid point of `B Cdot`

Explanation

According to the question, we have tetrahedron as show in fig 2.12
`vec(AD)=2sqrt2hati-2hatk`
` and vec(OE)=3sqrt2hati+sqrt6hatj`
cosine of angle between the vectors is
`costheta=12/(sqrt12sqrt24)`
`1/sqrt2`