Try converting everything on the left-hand side to sines and cosines.
The first fraction should simplify as (cos^2(A))/(cos(A) - sin(A)).
The second fraction should simplify as (sin^2(A))/(sin(A) - cos(A)).
Note that sin(A) - cos(A) = -[cos(A) - sin(A)], and combine the fractions.
Factor the difference of squares in the numerator. Cancel the common factor.
What are you left with? :wink: