1. **Problem Statement:** We have an isosceles triangle inscribed in a circle with two equal sides meeting at the top vertex called the "centre." The angles at the base are labeled $y$ (left) and $x$ (right). We need to find $y$ in terms of $x$. 2. **Key Properties:** In an isosceles triangle, the angles opposite the equal sides are equal. Here, the two sides meeting at the centre are equal, so the base angles $x$ and $y$ are equal. 3. **Using Triangle Angle Sum:** The sum of angles in any triangle is $180^\circ$. So, $$x + y + \text{angle at centre} = 180^\circ$$ 4. **Since the triangle is isosceles with equal sides meeting at the centre, the base angles are equal:** $$x = y$$ 5. **Therefore, substituting $y = x$ into the angle sum:** $$x + x + \text{angle at centre} = 180^\circ$$ $$2x + \text{angle at centre} = 180^\circ$$ 6. **Without the exact value of the angle at the centre, the best we can say is:** $$y = x$$ **Final answer:** $$\boxed{y = x}$$