Find , when

Theorem: y and x are given in a different variable that is θ . We can find by finding and and then dividing them to get the required thing.

=

= e^θ (cosθ + sinθ ) + (sinθ -cosθ )e^θ ………..(1) {by using product rule, }

= e^θ (cosθ - sinθ ) + e^θ (sinθ + cosθ ) …………….(2) {by using product rule, }

Dividing (1) and (2), we get

=

=tanθ .