What is the equation of the circle which touches both the axes in the first quadrant and the line y - 2 = 0?

What is the equation of the parabola with focus (-3, 0) and directrix x - 3 = 0 ?

What is the distance between the foci of the ellipse x² + 2y² = 1 ?

Let a, b, c be the lengths of sides BC, CA, AB respectively of a triangle ABC. If p is the perimeter and q is the area of the triangle, then what is $p(p-2a) \tan \left(\frac{A}{2}\right)$ equal to ?