# Thread: Need help figuring out how to rewrite a system of equations

1. ## Need help figuring out how to rewrite a system of equations

Hello,

I'm doing a problem in static mechanics dealing with the sum of equilibrium forces.
The two equations I come up with are
EFx=T-Nsin20=0
EFy=Ncos20-mg=0

The goal is to solve for T, which has been given to me as T=(mgsin20)/cos20. My question is how does T equate to this? The example I am following along with gives the answer but not the steps required. It says to eliminate N to yield the previous equation for T but I do not understand how T can equal (mgsin20)/cos20. Is this even a system of equations problem or am I looking at it wrong to begin with? any help is appreciated!

2. ## Re: Need help figuring out how to rewrite a system of equations

What you gives depends upon some other relation between "EFx" and "EFy". I take those are components of vector EF. What are you told about EF?

3. ## Re: Need help figuring out how to rewrite a system of equations

$\displaystyle N =m*g/\text{Cos}[20]$

$\displaystyle T=N *\text{Sin}[20]\text{ }=m*g* \text{Sin}[20]/\text{Cos}[20] = m*g* \text{Tan}[20]$

4. ## Re: Need help figuring out how to rewrite a system of equations

ahhh I knew it had to be something as simple as that. I guess 3 hours of studying had fried my brain. Many thanks

5. ## Re: Need help figuring out how to rewrite a system of equations

Originally Posted by HallsofIvy
What you gives depends upon some other relation between "EFx" and "EFy". I take those are components of vector EF. What are you told about EF?
My fault for not clarifying the entire problem, I was just concerned with how to rewrite the equation to solve for T. Also the E's i wrote were to represent Sigma. Thanks for the reply though!