Cross Product Formula

The cross product or vector product is a binary operation on two vectors in three-dimensional space (R3) and is denoted by the symbol x. Two linearly independent vectors a and b, the cross product, a x b, is a vector that is perpendicular to both a and b and therefore normal to the plane containing them.
Cross Product FormulaCross Product is given by,

A×B=|ijka1a2a3b1b2b3|

Where,
a1, a2, a3 are the components of the vector
a
and b1, b2 and b3 are the components of
b
 .

Cross Product Formula is given by,

a×b=|a||b|sinθ

Cross product formula is used to determine the cross product or angle between any two vectors based on the given problem.

Solved Examples

Question 1:Calculate the cross products of vectors a = <3, 4, 7> and b = <4, 9, 2>.

Solution:

The given vectors are, a = (3, 4, 7) and b = (4, 9, 2)
The cross product is given by
×
b =
|ijka1a2a3b1b2b3|

×
b =
|ijk347492|

×
b =
i(4×29×7)j(3×24×7)+k(3×94×4)

a

×
b =
i(863)j(628)+k(2716)

×
b = 
55i+22j+11k

Question 2:

Find the angle between two vector a and b, where a =<-4, 3, 0> and b =<2, 0, 0>

Solution:

We know that, the formula to find the angle between two vectors is

Sin θ = a × b / |a| |b|

Therefore, θ = sin-1[a × b / |a| |b|]

Now, we have to find the cross product of two vectors and b:

a×b=|ijk430200|

= i (0) -j(0) +k(-6)

a × b = -6k

|a|=16+9+0=5

|b|=4+0+0=2

While finding the angle between two vectors, substitute the magnitude of the vector value, Thus,

|a × b| = 6

Therefore,  θ = sin-1[|a × b|/ |a| |b|]

θ = sin-1[ 6/ 5 .2 ]

θ = sin-1[ 3/ 5 ] = 36.87°

Hence, the angle between two vectors, a and b (θ) is 36.87°

To learn more problems, keep visiting BYJU’S – The Learning App and download the app to learn with ease.

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