Help me cause I’m failing math

Which of the following is not a subset of {1,2,3}?

Prove sin2a + cos2a - 1 / sin2a + cos2a + 1 = 1 - tana / 1 + cota

Which statements about the system are true? check all that apply. y =1/3 x – 4 3y – x = –7 the system has one solution. the system consists of parallel lines. both lines have the same slope. both lines have the same y–intercept. the equations represent the same line. the lines intersect.