Mark M. answered 10/23/16
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Retired math prof. Very extensive Precalculus tutoring experience.
6sin2x - 7cos2x = 1
Recall that sin2x + cos2x = 1. So, cos2x = 1 - sin2x.
The original equation can then be rewritten as: 6sin2x - 7(1-sin2x) = 1
13sin2x = 8
sin2x = 8/13
So, csc2x = 1/sin2x = 13/8