How do I this equation is not an identity? Write explanation in paragraph form (Siny+Cosy)²=Sin²y+Cos²y
An Identity is an algebraical expression with variables, where the expression remains true, no matter what the values variables take.
So, Here The expression is
The Left Hand Side, When expanded, is equal to:
But The Right Hand Side is equal to
So, This can't be an identity in any cost.