Respuesta :

Using trigonometric identities, sin^2(y) = 1 - cos^2(y).
If you substitute that in, you get 1- cos^2(y)/(1-cos(y)).
You can factorise 1 - cos^2(y) to be (1-cos(y))(1+cos(y)).
This means that the answer is 1 + cos(y) as the 1 - cos(y) will cancel. 

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