Find the angle between each of the following pairs of vectors A⃗ =Axi^+Ayj^ and B⃗ =Bxi^+Byj^.. Ax1= -3.20, Ay1= 4.40; Bx1= 2.70, By1= -3.10. i know this is dot prodoct but the calculater just keep saying error

Verified Answer :

The product point of the two vectors is given by:

\(A.B = (-3.20i + 4.40j). (2.70i - 3.10j)\)

\(A.B = (-3.20 * 2.70) + (4.40 * (- 3.10))\)

\(A.B = -8.64 -13.64\)

\(A.B = -22.28\)

Then, the module of both vectors is:

For vector A:

\(A = \sqrt{(- 3.20) ^ 2 + (4.40) ^ 2}\)

\(A = 5.44\)

For vector B:

\(B = \sqrt{(2.70) ^ 2 + (- 3.10) ^ 2}\)

\(B = 4.11\)

Finally the angle between the vectors is given by:

\(\alpha =Cos^{-1}(\frac{A.B}{|A||B|})\)

Substituting values:

\(\alpha =Cos^{-1}(\frac{-22.28}{|5.44||4.11|})\)

\(\alpha = 175\)

Answer:

The angle between the vectors is:

\(\alpha = 175\)

The angle between the \(\overrightarrow{A}\) and \(\overrightarrow{B}\) is \(\boxed{\bf 175^{\circ}}\).

Further explanation:

Concept used:

The dot product of \(\overrightarrow{A}\) and \(\overrightarrow{B}\) is calculated as follows:

\(\boxed{\overrightarrow{A}\cdot \overrightarrow{B}=|A||B|\ \text{cos}\theta}\)       …… (1)

Here, \(|A|\) and \(|B|\) are the magnitude of \(\overrightarrow{A}\) and \(\overrightarrow{B}\) respectively.

Calculation:

The vector \(\overrightarrow{A}\) can be written as follows:

\(\boxed{\overrightarrow{A}=A_{x}\hat{i}+A_{y}\hat{j}}\)....(1)

The vector \(\overrightarrow{B}\) can be written as follows:

\(\boxed{\overrightarrow{B}=B_{x}\hat{i}+B_{y}\hat{j}}\)....(2)

The value of \(A_{x}\) is \(-3.20\),\(A_{y}\) is \(4.40\), \(B_{x}\) is \(2.70\) and \(B_{y}\) is \(-3.10\).

Now, substitute the value of \(A_{x}\) and \(A_{y}\) in equation (1).

\(A=-3.20\hat{i}+4.40\hat{j}\)

Substitute the value of \(B_{x}\) and \(B_{y}\) in equation (2).

\(B=2.70\hat{i}-3.10\hat{j}\)  

The magnitude of vector \(\overrightarrow{A}\) can be calculated as follows:

\(\boxed{|A|=\sqrt{A^{2}_{x}+A^{2}_{y}}}\)              …… (3)

Substitute the value of \(A_{x}\) and \(A_{y}\) equation (3) to obtain the magnitude of vector \(\overrightarrow{A}\) as follows:

\(\begin{aligned}|A|&=\sqrt{(-3.20)^{2}+(4.40)^{2}}\\&=\sqrt{10.24+19.36}\\&=\sqrt{29.6}\\&=5.44\end{aligned}\)  

Similarly the magnitude of vector \(\overrightarrow{B}\) can be calculated as follows:

\(\boxed{|B|=\sqrt{B^{2}_{x}+B^{2}_{y}}}\)              ……(4)

Substitute the value of \(B_{x}\) and \(B_{y}\) equation (4) to obtain the magnitude of vector \(\overrightarrow{B}\) as follows:

\(\begin{aligned}|B|&=\sqrt{(2.70)^{2}+(-3.10)^{2}}\\&=\sqrt{7.29+9.61}\\&=\sqrt{16.9}\\&=4.11\end{aligned}\)  

Dot product of vector \(\overrightarrow{A}\) and vector \(\overrightarrow{B}\) can be calculated as follows:

\(\begin{aligned}\overrightarrow{A}\cdot \overrightarrow{B}&=\left(-3.20\hat{i}+4.40\hat{j}\right)\cdot \left(-3.20\hat{i}+4.40\hat{j}\right)\\&=(-3.20\cdot 2.70)-(4.40\cdot 3.10)\\&=-8.64-13.64\\&=-22.28\end{aligned}\)  

Substitute \(\overrightarrow{A}\cdot \overrightarrow{B}=-22.28\), \(|A|=5.44\) and \(|B|=4.11\) in the equation (1) to obtain the angle between \(\overrightarrow{A}\) and \(\overrightarrow{B}\) as follows:

\(\begin{aligned}-22.28&=(5.44)(4.11)\ \text{cos}\theta\\-22.28&=22.3584\ \text{cos}\theta\\ \text{cos}\theta&=-\dfrac{22.28}{22.3584}\\ \text{cos}\theta&=-0.996\end{aligned}\)

Further simplify the above equation as follows:

\(\begin{aligned}\text{cos}\ \theta&=-0.996\\ \theta&=\text{cos}^{-1}(-0.996)\\ \theta&=174.87\\ \theta &\approx175\end{aligned}\)

Therefore, the angle between the \(\overrightarrow{A}\) and \(\overrightarrow{B}\) is \(\boxed{\bf 175^{\circ}}\).

Learn more:

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Answer details:

Grade: Senior school

Subject: Mathematics

Chapter: Vector


Keywords: Vector, dot product, angle, magnitude, AB=AB cos(theta), cross product, degree, radian, Ax1=-3.20, Ay1=4.40, Bx1=2.70, By1=-3.10, pair of vectors, angle between A and B.