question_answer

If \[\vec{\lambda }\] is a unit vector perpendicular to plane of vector a and b and angle between them is q, then a . b will be                                                 [RPET 1985]

A)             \[|\mathbf{a}|\,\,|\mathbf{b}|\,\sin \theta \,\vec{\lambda }\]

B)             \[|\mathbf{a}|\,\,|\mathbf{b}|\,\cos \,\,\theta \,\vec{\lambda }\]

C)             \[|\mathbf{a}|\,\,|\mathbf{b}|\,\cos \,\,\theta \,\]

D)             \[|\mathbf{a}|\,\,|\mathbf{b}|\,\sin \theta \,\]