#1:
The left side, you can cross multiply into:
Use the identity:
Help!
1. Verify the identity: (1/1-cosx)-(cosx/1+cosx)=2csc(squared)x-1
2.Verify the identity: cos5t-cos3t= -8sin(squared)t(2cos(cubed)t-cost)
3. Verify the identity: 2cos4xsin2x=2sin3xcos3x-2cosxsinx