1. Cos3x + Sin4x = 0, 2. Tan2x = Tan( X + π/4 ), 3. Tan8x = Cot2x, 4. Tan3x = -Tanx, 5. 4cos^2x/2 - 3 = 0, 6. 4cos^2x( 5x + 2π/5 ) - cos^2( x/4 + π ) = 0