9 / (1 + cos x ) + 9 / ( 1 - cos x)
We can do this
9 ( 1 - cos x) 9 ( 1 + cos x)
_________________ + ___________________
(1 + cos x) (1 - cos x) (1 - cos x) ( 1 + cos x)
9 - 9 cos x + 9 + 9 cos x
______________________
1 - cos^2 x
18
_______
sin^2 x
18 * 1
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(sin x)^2
18 * [ 1 / sin x ] ^2
18 * [ csc x ] ^2
18 csc^2 x