Finding the x and y components of this vector

[kevnm67]

Hey guys,

I am not sure I did this problem correctly and would like some feedback. Below is how I reasoned through the problem. Thanks for your help.

Kevin

Homework Statement

Find x- and y-components of the vector (3.0 , - x-direction).

Homework Equations

cosθ= A/H
sinθ= O/H

H= -3.0

The Attempt at a Solution

I made two vectors connecting to form a 90 degree angle pointing at the hypotenuse. The other two angles are now 45 degrees and I plugged them into the above equations as follows:
cos(45)=A/-3 = -2.12
sin (45)=O/-3= -2.12

(-2.12)^2 + (-2.12)^2 = -3^2
8.99 or 9 = 9
So X and Y are both -2.12

 

[lewando]

Am I correct in reading that your original vector looks like this:

3 <----------------+

?

If so, I don't see much of a y-component.

 

[kevnm67]

Am I correct in reading that your original vector looks like this:

3 <----------------+

?

If so, I don't see much of a y-component.

yes. But isn't that the resultant vector? I solved two other prior to this question and they gave a magnitude and direction. To solve those, I made two vectors and solved for their side of the triangle. Is that not how I should be trying to solve this question? At first I thought it would be 0, but it's not, at least to my understanding, asking for the x and y coordinates of the line drawn above

 

[lewando]

This problem is a special case where the direction lies exactly along one of the axes, in which case there is no right triangle for you to construct. So your trig functions don't apply.

 

[kevnm67]

This problem is a special case where the direction lies exactly along one of the axes, in which case there is no right triangle for you to construct. So your trig functions don't apply.

So does that mean x= -3 and y=0?

 

[lewando]

That sounds right to me! Good luck with your coursework.

 

[kevnm67]

That sounds right to me! Good luck with your coursework.

Thanks for your help!