How to Determine Angles in Triangles Through the Side Angles
- 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.
Source...