How Should Angles Be Used in Calculating Tension Forces?

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The discussion focuses on calculating tension forces in a system involving three cables designated as T1, T2, and T3. The user attempts to find the x and y components of each tension using trigonometric functions but struggles with angle conventions and sign errors. Key issues include confusion over which angles to use for T2 and the correct signs for the equations representing the sum of forces. Clarifications are provided regarding angle conventions, emphasizing that the positive x-axis is 0 degrees and angles increase counterclockwise. The user ultimately realizes that dropping T1 in their calculations led to incorrect results, highlighting the importance of correctly applying trigonometric principles in equilibrium problems.
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Homework Statement


See attached figure below for problem:
CH4C WA.jpg

I'm designating the "horizontal cable" T1, the "incline cable" T2, and the "vertical cable" T3.

Homework Equations


I used the following to find x and y components of each force:
x comp=Tncos(theta)
y comp=Tnsin(theta)

The Attempt at a Solution



I made a chart for T1, T2, and T3 for the respective x and y components.
T1:
x=T1cos(180)
y=0 (because it's only the x direction)
I didn't know which angle to use for theta, I used 180 because of where I put the x and y-axis in my free body diagram.

T2:
x=T2cos(38)
y=T2sin(38)
Again, I didn't know if I should use the 38* or add 180 to it...

T3:
x=0 (because it's only in the y direction?)
y=532 N (given)

I started to sum my x components and then solve for T2, but the answer that I got was wrong. I did this:
Sun of x components: 0=T1cos(180)+T2cos(38)
T2=T1(cos(180)/cos(38))
T2=1.27 N
I tried both 38* and 218* for the theta of T2 and both answers were wrong.

Sum of y components: 0=T1sin(180)+T2sin(38)+532N
Once I got the correct value for T2, I would plug it into this equation to find T1. And T3 will equal the weight (532 N) because of equilibrium, right?

Can anyone help me get on the right track?

Thanks!
 
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cbchapm2 said:
Sun of x components: 0=T1cos(180)+T2cos(38)
T2=T1(cos(180)/cos(38))
You've switched the sign there.
T2=1.27 N
Where did that come from?
Sum of y components: 0=T1sin(180)+T2sin(38)+532N
To be consistent with the signs, that should be -532N (sin(270)=-1).
 
You have some confusion with angles. The convention is that the positive x- axis has angle 0 degrees, and the angle increases as one goes counterclockwise. Therefore, positive y is 90 degrees, negative x is 180 degrees and negative y is 270 degrees.
 
I got the right answer! When I solved the first equation for T2, I dropped the T1 and it threw off everything else too.
 
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