Find the cosine and sine angle between the vectors $\overrightarrow a = 2\widehat i + \widehat j + 3\widehat k$ and $\overrightarrow b = 4\widehat i - 2\widehat j + 2\widehat k$.
Answer
627.3k+ views
Hint: Here, we will use the formula of the dot product of two vectors. Then substituting the given vectors in the formula, we will be able to find the cosine angle between the given vectors. We will then substitute the cosine angle in the formula depicting the relationship between cosine and sine to find both the required angles between the given two vectors.
Formula Used:
We will use the following formulas:
1.$\overrightarrow a \cdot \overrightarrow b = \left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|\cos \theta $
2.${\sin ^2}\theta + {\cos ^2}\theta = 1$
Complete step-by-step answer:
Given vectors are:
$\overrightarrow a = 2\widehat i + \widehat j + 3\widehat k$
$\overrightarrow b = 4\widehat i - 2\widehat j + 2\widehat k$
Now, by dot product formula, we know that,
$\overrightarrow a \cdot \overrightarrow b = \left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|\cos \theta $
This can also be written as:
$ \Rightarrow \cos \theta = \dfrac{{\overrightarrow a \cdot \overrightarrow b }}{{\left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|}}$
Now, substituting the vectors, we get,
$ \Rightarrow \cos \theta = \dfrac{{\left( {2\widehat i + \widehat j + 3\widehat k} \right) \cdot \left( {4\widehat i - 2\widehat j + 2\widehat k} \right)}}{{\sqrt {{{\left( 2 \right)}^2} + {{\left( 1 \right)}^2} + {{\left( 3 \right)}^2}} \cdot \sqrt {{{\left( 4 \right)}^2} + {{\left( { - 2} \right)}^2} + {{\left( 2 \right)}^2}} }}$
$ \Rightarrow \cos \theta = \dfrac{{8 - 2 + 6}}{{\sqrt {4 + 1 + 9} \cdot \sqrt {16 + 4 + 4} }}$
Solving this further, we get,
$ \Rightarrow \cos \theta = \dfrac{{12}}{{\sqrt {14} \cdot \sqrt {24} }} = \dfrac{{12}}{{\sqrt {2 \times 7} \cdot \sqrt {2 \times 2 \times 2 \times 3} }}$
$ \Rightarrow \cos \theta = \dfrac{{12}}{{4\sqrt {21} }} = \dfrac{3}{{\sqrt {3 \times 7} }} = \dfrac{{\sqrt 3 }}{{\sqrt 7 }}$
Therefore, the cosine angle between the given vectors is $\cos \theta = \dfrac{{\sqrt 3 }}{{\sqrt 7 }}$
Now, we know that: ${\sin ^2}\theta + {\cos ^2}\theta = 1$
Hence, $\sin \theta = \sqrt {1 - {{\cos }^2}\theta } $
Substituting the value of $\cos \theta $, we get,
$\Rightarrow \sin \theta = \sqrt {1 - {{\left( {\dfrac{{\sqrt 3 }}{{\sqrt 7 }}} \right)}^2}} = \sqrt {1 - \dfrac{3}{7}} = \sqrt {\dfrac{4}{7}} $
Therefore,
$\Rightarrow \sin \theta = \dfrac{2}{{\sqrt 7 }}$
Hence, the cosine and sine angle between the vectors $\overrightarrow a = 2\widehat i + \widehat j + 3\widehat k$ and $\overrightarrow b = 4\widehat i - 2\widehat j + 2\widehat k$ are $\dfrac{{\sqrt 3 }}{{\sqrt 7 }}$ and $\dfrac{2}{{\sqrt 7 }}$ respectively.
Thus, this is the required answer.
Note: A scalar is a quantity that has a magnitude whereas; a vector is a mathematical quantity that has both magnitude and direction. A line of a given length and pointing along a given direction, such as an arrow, is a typical representation of a vector. Also, for further knowledge, position vector is also known as location vector, it is a straight line having one end fixed and the other end attached to a moving point, it is used to describe the position of a certain point, which turns out to be its respective coordinates.
Formula Used:
We will use the following formulas:
1.$\overrightarrow a \cdot \overrightarrow b = \left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|\cos \theta $
2.${\sin ^2}\theta + {\cos ^2}\theta = 1$
Complete step-by-step answer:
Given vectors are:
$\overrightarrow a = 2\widehat i + \widehat j + 3\widehat k$
$\overrightarrow b = 4\widehat i - 2\widehat j + 2\widehat k$
Now, by dot product formula, we know that,
$\overrightarrow a \cdot \overrightarrow b = \left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|\cos \theta $
This can also be written as:
$ \Rightarrow \cos \theta = \dfrac{{\overrightarrow a \cdot \overrightarrow b }}{{\left| {\overrightarrow a } \right|\left| {\overrightarrow b } \right|}}$
Now, substituting the vectors, we get,
$ \Rightarrow \cos \theta = \dfrac{{\left( {2\widehat i + \widehat j + 3\widehat k} \right) \cdot \left( {4\widehat i - 2\widehat j + 2\widehat k} \right)}}{{\sqrt {{{\left( 2 \right)}^2} + {{\left( 1 \right)}^2} + {{\left( 3 \right)}^2}} \cdot \sqrt {{{\left( 4 \right)}^2} + {{\left( { - 2} \right)}^2} + {{\left( 2 \right)}^2}} }}$
$ \Rightarrow \cos \theta = \dfrac{{8 - 2 + 6}}{{\sqrt {4 + 1 + 9} \cdot \sqrt {16 + 4 + 4} }}$
Solving this further, we get,
$ \Rightarrow \cos \theta = \dfrac{{12}}{{\sqrt {14} \cdot \sqrt {24} }} = \dfrac{{12}}{{\sqrt {2 \times 7} \cdot \sqrt {2 \times 2 \times 2 \times 3} }}$
$ \Rightarrow \cos \theta = \dfrac{{12}}{{4\sqrt {21} }} = \dfrac{3}{{\sqrt {3 \times 7} }} = \dfrac{{\sqrt 3 }}{{\sqrt 7 }}$
Therefore, the cosine angle between the given vectors is $\cos \theta = \dfrac{{\sqrt 3 }}{{\sqrt 7 }}$
Now, we know that: ${\sin ^2}\theta + {\cos ^2}\theta = 1$
Hence, $\sin \theta = \sqrt {1 - {{\cos }^2}\theta } $
Substituting the value of $\cos \theta $, we get,
$\Rightarrow \sin \theta = \sqrt {1 - {{\left( {\dfrac{{\sqrt 3 }}{{\sqrt 7 }}} \right)}^2}} = \sqrt {1 - \dfrac{3}{7}} = \sqrt {\dfrac{4}{7}} $
Therefore,
$\Rightarrow \sin \theta = \dfrac{2}{{\sqrt 7 }}$
Hence, the cosine and sine angle between the vectors $\overrightarrow a = 2\widehat i + \widehat j + 3\widehat k$ and $\overrightarrow b = 4\widehat i - 2\widehat j + 2\widehat k$ are $\dfrac{{\sqrt 3 }}{{\sqrt 7 }}$ and $\dfrac{2}{{\sqrt 7 }}$ respectively.
Thus, this is the required answer.
Note: A scalar is a quantity that has a magnitude whereas; a vector is a mathematical quantity that has both magnitude and direction. A line of a given length and pointing along a given direction, such as an arrow, is a typical representation of a vector. Also, for further knowledge, position vector is also known as location vector, it is a straight line having one end fixed and the other end attached to a moving point, it is used to describe the position of a certain point, which turns out to be its respective coordinates.
Recently Updated Pages
Write structures of the following compounds i 2 Chloro3methylpentane class 11 chemistry CBSE

What is BLO What is the full form of BLO class 8 social science CBSE

Explain the Treaty of Vienna of 1815 class 10 social science CBSE

A Paragraph on Pollution in about 100-150 Words

XIX+XXX A 49 B 51 C 55 D 44 class 5 maths CBSE

If x a + bt + ct2 where x is in meters and t is in class 11 physics CBSE

Trending doubts
One Metric ton is equal to kg A 10000 B 1000 C 100 class 11 physics CBSE

Find the value of the expression given below sin 30circ class 11 maths CBSE

What do you mean by retardation What is its SI uni class 11 physics CBSE

Draw a diagram of nephron and explain its structur class 11 biology CBSE

10 examples of friction in our daily life

Difference between physical and chemical change class 11 chemistry CBSE

