1. The problem statement, all variables and given/known data Without using tables(calculators) find the numerical value of Sin[Pi/8]^2 - Cos[3 (Pi/8)]^4 2. Relevant equations 3. The attempt at a solution I tried changing it to: 1-cos[pi/8]^2 - cos[3pi/8]^4 but have no idea where to go... its really got me scratching my head. Any ideas? Any help is much appreciated, thank you.