Resultant of two orthogonal vectors

In summary, the conversation discusses a problem with finding the value of sec θ in a given equation. The relevance of the equation is questioned and an alternative interpretation is suggested. Ultimately, the value of sec θ is found to be 3, assuming one vector is 2 times the magnitude of the other.
  • #1
Crystal037
167
7
Homework Statement
The resultant of two orthogonal vectors makes an angle θ with their difference. if magnitude of one is 2 times that of the other, find the value of sec θ.
Relevant Equations
|a+b|=sqrt(a^2 +b^2 +2ab)
IMG_20200327_160143.jpg

But the answer in my book is given that sec(theta) =3. Where am I going wrong?
 
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  • #2
Crystal037 said:
Where am I going wrong?
I think nowhere. So the book answer must be a mistake.
You could come up with a better drawing, though. And a sign of the secant is minus if b = 2a.
 
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  • #3
Maybe I am interpreting the question wrongly. I don't know if that is what the question is supposed to mean.
 
  • #4
You worked out your interpretation. You think there is an alternative ?
 
  • #5
Crystal037 said:
Homework Statement:: The resultant of two orthogonal vectors makes an angle θ with their difference. if magnitude of one is 2 times that of the other, find the value of sec θ.
Relevant Equations:: |a+b|=sqrt(a^2 +b^2 +2ab)
Your relevant equation is wrong, unless by ab, you mean the scalar product of vector a and vector b .

As far as a different reading of the problem (Yes, the given statement is ambiguous.):

Rather than one and the other referring to the two orthogonal vectors, perhaps they refer to the resultant and the difference vectors. Is this even possible?
 
  • #6
SammyS said:
Is this even possible?
If two vectors ##\vec a## and ##\vec b## are orthogonal, then ##\vec a\cdot\vec b=0 \Rightarrow |\vec a + \vec b | = |\vec a - \vec b | ##
 
  • #7
Stated differently, if the vectors are orthogonal, one can form a ##a\times2a## rectangle with them. One diagonal is the sum, the other is the difference and they have equal magnitudes. There are two angles between the diagonals to be considered, one being the supplementary of the other.
 
  • #8
One comment about your notation: when the problem says "the magnitude of one is 2 times that of the other", it's not correct to write ##\vec b = 2 \vec a##. That would imply that the two vectors are parallel to each other and not orthogonal.
 
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  • #9
Crystal037 said:
If magnitude of one is 2 times that of the other, find the value of sec θ.
Try this instead.

If magnitude of one is ##\sqrt{2~} ## times that of the other, find the value of sec θ.
 
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  • #10
SammyS said:
Try this instead.

If magnitude of one is ##\sqrt{2~} ## times that of the other, find the value of sec θ.
Yes then the answer comes as 3.
 

1. What is the definition of resultant of two orthogonal vectors?

The resultant of two orthogonal vectors is a vector that represents the combined effect of the two original vectors. It is found by using the Pythagorean theorem to calculate the magnitude and trigonometric functions to determine the direction.

2. How are the components of the resultant calculated?

The components of the resultant are calculated by using the dot product and cross product of the two original vectors. The dot product gives the magnitude of the resultant in the direction of one of the vectors, while the cross product gives the magnitude in the direction perpendicular to both vectors.

3. Can the resultant of two orthogonal vectors ever be zero?

Yes, the resultant of two orthogonal vectors can be zero if the two vectors are equal in magnitude but opposite in direction. This is known as a zero vector or a null vector.

4. How do you find the angle between two orthogonal vectors?

The angle between two orthogonal vectors can be found by using the inverse trigonometric functions of the dot product and cross product. The dot product gives the cosine of the angle, while the cross product gives the sine of the angle.

5. What are some real-life applications of the resultant of two orthogonal vectors?

The resultant of two orthogonal vectors is commonly used in physics and engineering, such as calculating the force of two perpendicular forces acting on an object. It is also used in navigation and mapping, as well as in computer graphics for creating 3D images and animations.

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