How to Determine Angles in Triangles Through the Side Angles

Triangles can be found everywhere.

Triangles can be found everywhere -- on napkins, in the architecture of buildings and sometimes even floating high up in the sky (assuming you believe in UFOs). They are basic geometric shapes composed of three lines connected to one another via three corners. Each line has a length and each corner has an angle. The beauty of triangles is that each and every part of a triangle -- every length, every angle -- is related to one another through the magic of mathematics.

Instructions

1. Recognize the relationships between a triangle's angles. The angles of every triangle add up to 180 degrees, which means that given triangle angles A, B and C, you know that A + B + C = 180 degrees.

2. Plug the values of the angles you know into the equation you derived in Step One. Given angles of 45 degrees and 60 degrees, for instance, the equation would read A + 45 + 60 = 180 degrees.

3. Solve for the remaining angle by using mathematics.

   Subtract 45 and 60 from both sides of the equation: A = 180 - 45 - 60.

   A = 75 degrees

   Thus, the value of the unknown angle is 75 degrees.

References

• Math is Fun: Triangles Contain 180 Degrees