# Thread: Finding an angle within this triangle

1. ## Finding an angle within this triangle

Hi,

All variables given in blue are known values. I am trying to calculate the angle X in terms of the variables I know. How can I do this?

2. ## Re: Finding an angle within this triangle

Hello, Corpsecreate!

All variables given in blue are known values.
I am trying to calculate the angle X in terms of the variables I know.

The sum of the (interior) angles of a triangle is always equal to 180o.

Hence: .$\displaystyle A + B + (C + X) \;=\;180$

Got it?

3. ## Re: Finding an angle within this triangle

You can calculate the angle between the side$\displaystyle b$ and the horizontal, add $\displaystyle X$ to that and you have the angle $\displaystyle C.$

4. ## Re: Finding an angle within this triangle

Originally Posted by Soroban
Hello, Corpsecreate!

The sum of the (interior) angles of a triangle is always equal to 180o.

Hence: .$\displaystyle A + B + (C + X) \;=\;180$

Got it?
Angle $\displaystyle C$ is the entire interior angle, not just the angle up to the horizontal. $\displaystyle A + B + C$ will give $\displaystyle 180$, $\displaystyle A + B + (C + X)$ will give a number larger than $\displaystyle 180$.

Originally Posted by BobP
You can calculate the angle between the side$\displaystyle b$ and the horizontal, add $\displaystyle X$ to that and you have the angle $\displaystyle C.$
The angle side $\displaystyle b$ makes with the horizontal is $\displaystyle A + phi$, I dont see how adding $\displaystyle X$ to this angle would give me angle $\displaystyle C$?

NVM: Question has been solved!

5. ## Re: Finding an angle within this triangle

The angle side $\displaystyle b$ makes with the horizontal is $\displaystyle A + phi$, I dont see how adding $\displaystyle X$ to this angle would give me angle $\displaystyle C$?
NVM: Question has been solved!
The angle referred to is the complement of the one you state, that is, $\displaystyle 180 - (A+\phi).$

This will equal the angle below the horizontal at $\displaystyle C.$ Add $\displaystyle X$ and you get $\displaystyle C.$

BTW., some labels on the diagram would have helped.