Ellipse

If the tangent at a point \(\left( {4\cos \phi ,{{16} \over {\sqrt {11} }}\sin \phi } \right)\) to the ellipse \(16{x^2} + 11{y^2} = 256\) is also a tangent to \({x^2} + {y^2} - 2x = 15\), then \(\phi\) equsls