Hello,

I have a sinusoid curve in an euclidian orthonormal plane [OX,OY].

the equation of the curve is y=a sin x.

Now, I want to get the equation of the curve when I rotate it by an angle with respect to the (ox) axis like it is shown in the figure submitted.

To do that,I'll define tehe vectorial euclidian rotation :in an oriented vectorial euclidian plan, a vectorial rotation is simply defined by its angle . Its matrix in an orthonormal direct basis is :

In another way, a vector (x,y) has as image the vector (x',y') that can be calculated like that :

then we have :

and

as we have

, then we have

the problem is that I must write in function of .

Thank you for reading me. I'll be vey glad if you can help me