How do you work these out?
sec u- 1 / 1-cos u = sec u
sec x-cos x= sin x tan x
1/sin x - 1/csc x= csc x - sin x
remember that sec u = 1/cos u
and that csc u = 1/sin u
then for example
(1/cos u - 1) = 1
------------- -------
(1 - cos u) cos u
multiply both sides by cos u
(1 - cos u) = cos u
----------- -------
(1 - cos u) cos u
or
1 = 1 sure enough
for the second one, write sec as 1/cos and write tan as sin / cos
then multiply both sides by cos
and remember that sin^2 + cos^2 = 1
for the third one write csc is 1/sin