-xtanydy=ln(cosy)dx
-siny/cosy*1/ln(cosy)*dy=dx/x
1/cosy*1/ln(cosy)*d(cosy)=dx/x
d(ln(cosy))/ln(cosy)=dx/x
ln|ln(cosy)|=ln|x|+C
ln(cosy)=Cx
cosy=e^(Cx)
y=arccos(e^(Cx))