1. The problem statement, all variables and given/known data 1. (sinx - cosx)(sinx + cosx) = 2sin^2x-1 2. (2sinx + 3cos)^2 + (3sinx - 2cosx)^2 = 13 2. Relevant equations N/A 3. The attempt at a solution For 1. L.S. = sinx^2+sinxcosx-sinxcosx-cosx^2, the sinxcosx cancels and I'm lost. I haven't a clue how to do the second one. I missed a couple of day of school because of the flu before christmas break, so I need to understand this. Some please help.