Guys, i swear im going to fail functions this year T_T

I've been paying attention in class, but i dont get what the teacher is saying at all.

Were supposed to prove that these 2 things are equal.

Can someone pleeease show me how to do this?

because ive tried mixing them around but its not working at all.

so heres the question i have to prove

1 - (sin^2 y)/(1+(1/tan y)) - cos^2 y/1+tan y = sin y cos y

the teacher also wrote

recall: tan y = sin y/cos y

sin^2 y + cos ^2 y = 1

id really appreciate some help T_T thanks so much guys