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find the acute angle lies between the vectors a=3i+4j and b=7i+j

Sagot :

Answer:

The acute angle lies between the vectors a=3i+4j and b=7i+j is 45°

Explanation:

The given vectors are:

a = 3i + 4j

b = 7i + j

The acute angle between vectors a and and b is given by the formula:

[tex]\theta=\cos ^{-1}\frac{a.b}{|a\mleft\Vert b\mright|}[/tex]

The scalar product of vectors a and b is:

a.b = (3i + 4j).(7i + j)

a.b = (3x7) + (4x1)

a.b = 21 + 4

a.b = 25

The magnitude of a is:

[tex]\begin{gathered} |a|=\sqrt[]{3^2+4^2} \\ |a|=\sqrt[]{9+16} \\ |a|=\sqrt[]{25} \\ |a|=5 \end{gathered}[/tex]

The magnitude of b is:

[tex]\begin{gathered} |b|=\sqrt[]{7^2+1^2} \\ |b|=\sqrt[]{49+1} \\ |b|=\sqrt[]{50} \\ |b|=5\sqrt[]{2} \end{gathered}[/tex]

Substituting the values of a.b, |a|, and |b| into the formula for the acute angle.

[tex]\begin{gathered} \theta=\cos ^{-1}\frac{a.b}{|a\Vert b|} \\ \theta=\cos ^{-1}\frac{25}{5\times5\sqrt[]{2}} \\ \theta=\cos ^{-1}\frac{25}{25\sqrt[]{2}} \\ \theta=\cos ^{-1}\frac{1}{\sqrt[]{2}} \\ \theta=45^0 \end{gathered}[/tex]

Therefore, the acute angle lies between the vectors a=3i+4j and b=7i+j is 45°