(secx−1)(secx+1)2secx soi
B1 for adding the two fractions.
sec2x−12secx
B1 dep on previous B1 for expanding and simplifying the denominator.
tan2x2secx or tan2xcosx2
B1 dep on previous B1 for use of sec2x=1+tan2x.
tanx2secx×cotx or sin2x2cosx oe or tanxsinx2, leading to 2cosecxcotx AG
B1 dep on previous B1 with at least one more correct step to get to the given answer.
Alternative method:
cosx1−11+cosx1+11=1−cosxcosx+1+cosxcosx
(B1)
=1−cos2xcosx+cos2x+cosx−cos2x
(B1) dep on previous B1 for adding the two fractions.
=sin2x2cosx
(B1) dep on previous B1 for use of sin2x=1−cos2x.
=2cosecx×sinxcosx=2cosecxcotx AG
(B1)