How Do You Find a Missing Angle in a Triangle?

1. The Triangle Sum Theorem says that the three angles of a triangle will always add up to 180°
2. So we can add our three angles together and set them equal to 180° to solve for x
1. Angle SFN measures 81.3°
2. Angle FSN measures 54.9°
3. Angle FNS, our missing angle, is x
1. We can plug the values we know into our equation to solve for x
1. Simplify by adding the decimals on the left hand side
2. Then subtract 136.2 from both sides to get x by itself

Find the value of x in the figure below