Fl ifx is perpendicular to the vectors yi, y2 and y3 then x is also perpendicular to yı y and . [t to yi — у2 + уз- 2. [t f] if |x| 3 and |ly|= 4 and x is perpendicular to y then ||x +y||= 5. 3. [t fl let a be an invertiblen xn matrix, b be an n x n matrix and i be an n xn identity matrix then (aba1 i) = a(b i)a-1