1. The problem statement, all variables and given/known data I want to proove the determinant of the following 3x3 matrix is 0. 1 1 1 tanA tanB tanC tan2A tan2B tan2C where A+B+C=2pi. 2. Relevant equations Sorry I don't know how to type here so I show in the attachment. 3. The attempt at a solution Sorry I have attempted but found no way closed to the solution.