Vectors \[3\vec{a}-5\vec{b}\] and \[2\vec{a}+\vec{b}\] are mutually perpendicular. If \[\vec{a}+4\vec{b}\] and \[\vec{b}-\vec{a}\] are also mutually perpendicular, then the cosine of the angle between \[\vec{a}\] and \[\vec{b}\] is

Vectors \[3\vec{a}-5\vec{b}\] and \[2\vec{a}+\vec{b}\] are mutually pe

1.	Vectors \[3\vec{a}-5\vec{b}\] and \[2\vec{a}+\vec{b}\] are mutually perpendicular. If \[\vec{a}+4\vec{b}\] and \[\vec{b}-\vec{a}\] are also mutually perpendicular, then the cosine of the angle between \[\vec{a}\] and \[\vec{b}\] is
A.	\[\frac{19}{5\sqrt{43}}\]
B.	\[\frac{19}{3\sqrt{43}}\]
C.	\[\frac{19}{2\sqrt{45}}\]
D.	\[\frac{19}{6\sqrt{43}}\]
Answer» B. \[\frac{19}{3\sqrt{43}}\]

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Vectors \[3\vec{a}-5\vec{b}\] and \[2\vec{a}+\vec{b}\] are mutually perpendicular. If \[\vec{a}+4\vec{b}\] and \[\vec{b}-\vec{a}\] are also mutually perpendicular, then the cosine of the angle between \[\vec{a}\] and \[\vec{b}\] is

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