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

Got it?

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

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

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

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

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

NVM: Question has been solved!

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

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

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

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