Question 998939
cos y/ 1-tan y+ (sin y/1-cot y)=sin y +cos y 


{{{ cosy/(1-(siny/cosy)) + (siny/(1-cosy/siny))}}}


{{{cosy/((cosy-siny)/cosy) + (siny/((siny-cosy)/siny))}}}



{{{(cos^2(y)/(cosy-siny))+ ( sin^2(y)/(siny-cosy))}}}



{{{(cos^2(y)/(cosy-siny))- ( sin^2(y))/(cosy-siny))}}}


{{{(cos^2(y)-sin^2(y))/(cosy-siny)}}}


{{{((cosy+siny)(cosy-siny))/(cosy-siny)}}}


=cosy +siny