1. is equivalent to the limit of x at tanx, which is equivalent to 1 because it is infinitesimal.

2. divide sin(x 1+x2) by sinx1cosx2+cosx1csinx2, and then the integer absolute value becomes sinx1cosx2+(cosx1-) sinx2. Then take a 2 to become 2 times 0.5 sin (0.5x1) cos (0.5x1) cosx2-0.5( 1-cosx 1) sinx2, and then take 0.5 (1-cosx/).