If a→and b→  are perpendicular , thena→×a→×a→×a→×b→  is equal to :

Given a→and b→ are perpendicular, so that a¯⋅b¯=0Givena¯×a¯×a¯×a¯×b¯=a¯×a¯×a¯⋅b¯a¯−a¯⋅a¯b¯=a¯×a¯×0¯−|a¯|2b¯=−a¯2a¯×a¯×b¯=−a¯2a¯⋅b¯a¯−a¯⋅a¯b¯=−a¯2−a¯2b¯=a¯4b¯