If a and b are two unit vectors such that $$a+2b$$ and $$5a$$−$$4b$$ are perpendicular to each other then the angle between a and b is

Question

If a and b are two unit vectors such that $$a+2b$$ and $$5a$$−$$4b$$ are perpendicular to each  other then the angle between a and b is

Infinity Learn · Accepted Answer

Since the vectors $$a+2b$$  and $$5a$$−$$4b$$ are perpendicular so        $$a+2b.5a$$−$$4b=0$$⇒ $$5a2+6a$$·b−$$8b2=0$$⇒                               $$6a$$·$$b=3a=b=1$$⇒a·$$b=12$$⇒$$cos$$θ$$=12a=b=1$$⇒                                         θ$$=600$$

$If a and b are two unit vectors such that a + 2 b and 5 a - 4 b are perpendicular to each$ $other then the angle between a and b is$

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If a and b are two unit vectors such that a+2b and 5a−4b are perpendicular to each other then the angle between a and b is

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$If a and b are two unit vectors such that a + 2 b and 5 a - 4 b are perpendicular to each$ $other then the angle between a and b is$