The given vectors are | a → | b → +| b → | a → and | a → | b → −| b → | a → .
If two vectors are perpendicular to each other, then their dot product is zero.
The dot product of | a → | b → +| b → | a → and | a → | b → −| b → | a → is,
( | a → | b → +| b → | a → )⋅( | a → | b → −| b → | a → )=( | a → | b → )⋅( | a → | b → −| b → | a → )+( | b → | a → )⋅( | a → | b → −| b → | a → ) =( | a → | b → )⋅( | a → | b → )−( | a → | b → )⋅( | b → | a → )+( | b → | a → )⋅( | a → | b → )−( | b → | a → )⋅( | b → | a → ) = | a → | 2 | b → | 2 − | b → | 2 | a → | 2 =0
Hence, | a → | b → +| b → | a → is perpendicular to | a → | b → −| b → | a → .
Show that is perpendicular to, for any two nonzero vectors