# math

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given that vectors(p+2q) and (5p-4q) are orthogonal,if vectors p and q are the unit vectors,find the dot product of vectors p and q?

• math -

we know that
(p+2q)•(5p-4q) = 0
5p•p + 10p•q - 4p•q - 8q•q = 0
since p and q are unit vectors, we have
5 + 6p•q - 8 = 0
p•q = 1/2

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